During the operation of the electric furnace, production accidents are direct factors affecting product quality, output, economic benefits and personnel safety. Common accidents include electrode accidents, furnace leakage accidents, water cooling system failures and material overturning accidents. By analyzing the causes and treatments of these accidents, it can be found that many accidents can be avoided.
Electrode accident
Common faults of electrode system mainly include: electrode soft break, electrode hard break, electrode paste flow, copper tile arcing, electrode tripping, grounding blasting, electrode sliding down, electrode can not be pressed down and electrode can not be pulled out.
- Copper tile arcing
a. Cause
Ⅰ. There is no electrode paste in a section of copper tile.
Ⅱ. Copper tile is too loose.
Ⅲ. The electrode shell is deformed, resulting in poor contact between the electrode and copper tile.
b. Treatment method
If the electrode is suspended, the suspension should be handled. If the copper tile is too loose or the electrode shell is partially deformed, it is necessary to adjust the upper and lower gate rings and press the electrode.
- Electrode paste flow
a. Causes
Electrode paste flow is caused by arcing of copper tiles through the electrode shell or poor welding of the electrode shell to form holes.
b. Treatment methods
When the electrode paste flow is slight, the load can be appropriately reduced to continue roasting; when the paste flow is severe, the part where the paste flow occurs needs to be blocked and the electrode shell needs to be repaired by welding.
- Electrode hard break
a. Causes
Electrode hard break refers to the electrode breaking at the part that has been baked. The main reasons for the hard break of the plate are:
Ⅰ. The electrode is severely oxidized and the electrode diameter becomes smaller.
Ⅱ. The paste surface of the electrode is low after baking, and the newly added electrode paste is not sintered well with the baked electrode.
Ⅱ. Dust enters after the furnace is stopped, and the electrode is layered.
b. Treatment method
After the electrode is hard broken, it should be treated differently according to different situations: if the hard break is within 400mm, it can be pressed and released and continue to supply power. If the hard break is relatively long, it needs to be pressed and released gradually, and the other two electrodes are powered. After the electrode is baked long enough, power can be supplied again.
- Soft break of electrode
a. Cause
Soft break of electrode means that the break is in the part that has not been baked. The main reasons for soft break of electrode are:
Ⅰ. The electrode shell is not welded well, which reduces the conductive area of the weld and increases the current density.
Ⅱ. The electrode paste flow is not handled in time to form gaps.
Ⅲ. The electrode slides down and is not lifted in time.
Ⅳ. The electrode is not round and the current distribution of the copper tile is uneven.
b. Treatment method
After the electrode is hard broken, the bottom of the electrode shell needs to be re-welded, and the electrode paste is added to 1.700m for baking. After baking, the power is normally supplied.
Furnace leakage accident
Furnace runaway usually refers to an accident in which a large amount of low-nickel matte is rushed out of the furnace due to the failure to block the discharge port in front of the furnace and its surroundings. Slag runaway at the back of the furnace is relatively rare.
- Causes
The causes of furnace runaway are:
a. Overheating of the melt.
b. Severe corrosion of the lining and lining bricks.
c. The installation and maintenance of the discharge port in front of the furnace are not carried out as required.
d. The preparation work is not done well.
e. Unskilled technology and improper matte discharge operation.
- Treatment methods
a. In the early stage of furnace runaway, manpower should be organized to block the chute, keep the chute unobstructed, and transport low-nickel matte to the matte bag in time.
b. In the case of large furnace runaway, emergency measures should be taken, the electrode should stop supplying power, the slag should be quickly discharged at the back of the furnace to reduce the melt pressure, and the material should be pressed more by the material pipe in front of the furnace to reduce the melt temperature.
c. When there is no hope of blocking, the cooling water of the copper cooling water jacket in front of the furnace should be closed, and the personnel should be evacuated to allow the low-nickel matte to flow into the safety pit.
d. The discharge port after running the furnace should be thoroughly checked, especially the lining bricks and water cooling parts that need to be replaced must be replaced, and the lining must be reinstalled. After the treatment, resume production.
Furnace leakage accident
Leaking furnaces can be classified into matte and slag leakage due to different locations, and are more common at the junction of the side wall and the furnace bottom arch. Leaking matte has a great impact and is very easy to burn the enclosure, bottom plate, column, tie rod, spring and other components. Large leaking furnaces have greater losses.
- Causes
a. The composition of the slag changes or the grade of low nickel matte decreases.
b. High load and low slag return and ingredients cause overheating of slag and nickel matte.
c. The electrode is inserted too deep into the slag layer, causing nickel matte to overheat.
d. The furnace lining bricks are severely corroded.
e. Water-cooled parts leak and bricks are powdered.
- Treatment methods
a. When the leakage is small, the load and copper surface can be reduced, and the accident point can be ventilated and cooled or blocked with yellow mud.
b. When the leakage is large, the electrode is first powered off and the slag and matte are quickly discharged, and the furnace is charged with materials to reduce the temperature.
c. When dealing with leaking matte, it is strictly forbidden to pour water to avoid blasting and injuring people. In the later stage of leaking slag, water can be poured to cool it down. After the leaking furnace is dealt with, the furnace body should be inspected and identified, and the furnace can be started for production after repair.
Water cooling system failure
The furnace body of the depleted electric furnace is cooled by water. Failure of the water cooling system often occurs, and improper handling will cause serious consequences.
Due to the existence of slag return operation, the leakage of water-cooled parts in the depleted electric furnace is more dangerous than other furnaces without slag return, so more caution should be exercised in handling operations. Water-cooled parts leak, including leakage of cooling copper water jackets, water-cooled beams, electrode copper tiles, water-cooled flues, etc. It is not terrible for water-cooled parts to leak outside the furnace body, but the leakage accumulates in the furnace. When the electrode is inserted or slag is returned, the melt is strongly stirred, and the water flows to the lower part of the melt. When it encounters the molten matte, an explosion accident will occur in the furnace. In the case of light damage to the furnace top, in the case of heavy damage to the furnace body and the skeleton, and may cause casualties.
- Reasons
a. The copper water jacket process hole leaks, the processing quality is poor, the pressure acceptance is not serious, and it is not carried out according to regulations.
b. The water-cooled parts were cut off from water for a long time without being discovered in time. When the temperature of the water jacket was very high, water was suddenly supplied, and the water jacket leaked after being subjected to rapid cooling and rapid heating shock.
c. The water jacket was burned by low-nickel matte and leaked.
d. The water-cooled beam was burned, and the buried copper pipe leaked.
e. The copper tile was arced and caused the copper tile to leak.
- Treatment method
a. If a leak is found outside the furnace body, the leaking part must be found out. If the leaking part is not confirmed, production should be stopped; if it can be confirmed that the leak will not leak into the furnace, it can be handled while production is in progress, and it must be handled thoroughly.
b. If water is found in the furnace, the slag return and feeding should be stopped immediately, and the electrode should not be operated to disconnect the power supply to prevent the melt from stirring and exploding; immediately organize to find the leaking point, and turn off the water supply after finding the leaking point. After the leaking point is handled, wait for the accumulated water in the furnace to evaporate and then resume normal production.
Overturning accident
When the water content of the material added to the depleted electric furnace is too high, the water content of the material pile embedded in the melt evaporates violently, or when the material slope is too high and the slag layer is thin and the matte layer is thick, the material pile is embedded too deeply, and a rapid reaction occurs when it contacts the matte layer. The released SO2 and other gases cannot be discharged, resulting in a vicious material overturning.
- Causes
a. The water content of the added material is too high.
b. Too much material is added and the material slope is too high.
c. The surface temperature of the melt in the furnace is too high.
- Treatment methods
When overturning occurs, the material and even the melt will spray out from the holes of the furnace body. The on-site personnel should quickly evacuate the furnace body, especially the top of the furnace. After overturning, the facilities around the furnace body should be checked, because the high-temperature flue gas and melt spraying during overturning may cause the surrounding combustibles to catch fire, especially the electrode hose, etc. If a fire is found, it should be extinguished immediately.
The key to avoiding overturning accidents is prevention. First, the water content of the material should be checked when adding materials, and materials with high water content should not be added; second, the principles of frequent addition, small addition, and uniform addition should be strictly implemented when adding materials, and the material slope should be controlled.
