This paper makes a detailed analysis of the hard and soft breaking of electrode.
China's calcium carbide industry has become an important basic chemical raw material industry after more than 80 years of development.
In recent years, driven by the rapid development of the domestic economy and the growing demand for calcium carbide in the downstream, the domestic calcium carbide production capacity has expanded rapidly. In 2012, there were 311 calcium carbide enterprises in China, whose output has reached 18 million tons.
In the calcium carbide furnace equipment, the electrode is one of the important equipment, plays the role of conduction and heat transfer.
In the production of calcium carbide, electric current is input into the furnace through the electrode to generate electric arc, and the electric resistance heat and the electric arc heat are used to release energy (the temperature is up to about 2000℃) for calcium carbide smelting.
The normal operation of the electrode depends on the quality of the electrode paste, the quality of the electrode shell, the quality of welding, the length of the pressing time, the length of the electrode operation and other factors.
In the process of using the electrode, the operator's operation level is relatively strict requirements, careless operation is prone to lead to electrode soft, hard break accident, affect the transmission and conversion of electricity, resulting in furnace condition deterioration, and may even cause mechanical and electrical equipment damage, threatening the safety of the operator's life.
1. Cause analysis of soft fracture of calcium carbide furnace electrode
The sintering speed of the electrode is lower than the consumption speed, and the unfired electrode will cause the electrode to be soft broken after it is put down.
The specific reasons for the soft break of the electrode are as follows:
1.1 poor electrode paste quality and excessive volatile content.
1.2 the electrode case is too thin or too thick.
Too thin to withstand the external larger force and break, resulting in the electrode tube folded or leakage paste and soft break;
Too thick will cause the iron shell and electrode core contact is not close and string core, will also cause a soft break.
1.3 poor production of electrode iron shell or poor welding quality, resulting in rupture, resulting in leakage of paste or soft fracture.
1.4 the electrode pressure is passed frequently, the interval time is too short, or the electrode is too long after the electrode is lowered, resulting in soft break.
1.5 if the electrode paste is not added in time and the electrode paste is too high or too low, the electrode will be soft broken.
1.6 electrode paste block over large, careless when adding paste, on the rib board and put on stilts, can cause soft break.
1.7 electrode sintering is not good. When the electrode is lowered and after the electrode is lowered, the current cannot be properly controlled. As a result, the current is too large and the electrode shell is burned, resulting in the electrode soft breaking.
1.8 when the electrode lowering speed is greater than the sintering speed, and the paste segment in the shaping is exposed, or is about to expose the conductive element, the electrode shell will bear all the current and generate a large amount of heat. When the electrode shell is heated to more than 1200℃ and the tensile strength is reduced to the point where it cannot bear the dead weight of the electrode, a soft breaking accident will occur.
2. Cause analysis of hard fracture of calcium carbide furnace electrode
When the electrode is hard broken, if the molten calcium carbide is splashed, the operator has no protective measures, not timely evacuation may cause scalding accident.
The specific reasons for the electrode hard breaking include:
2.1 the electrode paste is not kept properly at ordinary times, the ash content is too high, more impurities are brought into the electrode paste, the electrode paste contains too little volatile content, premature sintering or poor adhesion, causing the electrode to break hard.
2.2 the electrode paste ratio is different, the binder proportion is small, the mixture is uneven, the electrode strength is poor, and the binder is not suitable. After the electrode paste is melted, the coarse and fine particles are layered, which reduces the electrode strength and can cause the electrode to be hard broken.
2.3 many times of power failure, frequent stop-start and stop-start. When power failure occurs, no necessary measures are taken, resulting in electrode cracking and sintering delamination.
2.4 more dust will fall into the electrode shell, especially after a long time of shutdown, a thick and thick layer of ash will accumulate in the iron shell of the electrode.
2.5 if the power outage lasts for a long time, the electrode working section is not buried in the charge and is seriously oxidized, which will also cause the electrode to be hard broken.
2.6 the electrode is subjected to sudden cooling and sudden heat, resulting in great difference in internal stress;
For example, the temperature difference between electrodes inserted into and out of the material during maintenance;
The temperature difference between inside and outside contact element is large.
Uneven heating during transmission may cause a hard break.
2.7 the electrode works too long and the tension is too large, which is a burden to the electrode itself. If the operation is careless, it may cause hard fracture.
2.8 too little air flow from the electrode holder tube or too little cooling water caused by the wind stop, resulting in excessive melting of the electrode paste, like water, so that the carbon particles precipitate, affecting the sintering strength of the electrode, causing the electrode to hard break.
2.9 the high current density of the electrode may cause the electrode to be hard broken.
