calcium carbide smelting electrode paste
Determination of specific resistance during the baking process of calcium carbide smelting electrode paste
Place the corundum crucible containing the sample of calcium carbide smelting electrode paste in a silicon-carbon rod electric furnace, and heat up at a rate of 100°C per hour. Use a bridge to measure the corresponding temperature through a pair of metal plates preliminarily fed into the smelting electrode paste. The resistance value of the electrode paste below is calculated and corrected with the container coefficient calibrated with 0.1N potassium chloride standard solution in advance, and then the specific resistance value of the calcium carbide smelting electrode paste at this temperature can be calculated.
Through this experiment, we can see the following problems:
(1) In the past, although it was known that the conductivity of the calcium carbide smelting electrode paste was poor before firing, it was still used to regard the calcium carbide smelting electrode paste as a conductor. According to the measurement results, it can be concluded that the calcium carbide smelting electrode paste before 400℃ is basically an insulator. Taking standard paste and special paste as examples, the specific resistance value at low temperature is very large, and it is not under the working conditions of electric furnace. There may be current passing through.
To prove this problem, we used a plastic tube with a diameter of 100m/m and a length of 300m/m to fill the calcium carbide smelting electrode paste with different granularities. The milliamp current shall prevail, and the voltage shall be recorded.
According to the different particle size, a calcium carbide smelting electrode paste column with a diameter of 100 m/m and a length of 300 m/m needs a voltage of 140-260 volts to start current flow, which shows that the conductivity is poor.
(2) From the test results of the special paste and the standard paste, it can be seen that the difference between the two is that the special paste has a lower specific resistance value before 500°C, but gradually tends to be the same after 500°C. Examples of specific resistance changes in the baking process of standard paste and special paste are shown in the following table. It can be seen that the airtight paste is significantly better than the standard paste at low temperatures. Therefore, the crucible is small, and the amount of calcium carbide smelting electrode paste sample is less (1100 grams) per firing. Therefore, the characteristics of fast heat conduction speed and strong self-sintering ability of special paste are not easy to show in small-scale experiments. However, considering that most of the special paste formulations use graphitized coke with better heat transfer, its thermal conductivity during the sintering process is definitely better than that of the standard paste, so the superiority of using the special paste under the conditions of electric furnace production will be better than that of the small-scale test. More prominent. A professor in Beijing once introduced the experience: that is, when the sintering speed of the electrode is lower than the consumption rate of the electrode, the less sintered the electrode and the faster the consumption, the electrode is in a dangerous state. At this time, if a small amount of graphite fragments are mixed into the calcium carbide smelting electrode paste, the sintering speed of the electrode can be greatly accelerated, the consumption of the electrode will be slowed down, and the working condition will be improved.