Metallurgical coke is most commonly used as a reducing agent for ferrosilicon smelting. Metallurgical coke is coke formed at a coking temperature of 1100 to 1300°C during the coking process, so it is also called high-temperature coke or full coke. Coke formed at a coking temperature of 600 to 800°C is called low-temperature coke or semi-coke. Gas coke is a kind of low-temperature coke. The so-called gas coke is a by-product of gas extraction.
The properties of gas coke and metallurgical coke are compared as follows:
1.Resistance
The relationship between resistivity and temperature of different cokes with a particle size of 10 to 15 mm is shown in Figure 4 based on actual measurements. The resistance of gas coke is higher than that of metallurgical coke. Even at higher temperatures, its resistance is still higher than that of metallurgical coke. An important advantage of gas coke is its high resistance. Practice has shown that ferrosilicon smelting uses a part of the gas coke, and the electrode can be inserted deeper into the charge, which can reduce electricity consumption.
2.Chemical composition
Gas coke contains less fixed carbon and more ash, and in terms of chemical properties, it is not as good as metallurgical coke. This is due to the low coking temperature of gas coke. The carbon content of gas coke is low, so when using it as a reducing agent, it is necessary to add more carbon. At the same time, due to the high ash content of gas coke, the amount of slag in smelting increases. On the other hand, due to the low carbon content of gas coke, its mechanical strength is low. During smelting, there is often a lack of carbon in and under the crucible. As can be seen, gas coke is used as a reducing agent in ferrosilicon smelting, and the condition of the furnace is difficult to maintain.
3. Porosity and Reactivity
The porosity of gas coke is 40-60% that of metallurgical coke. This not only increases the resistance of gas coke, but also expands the reaction area. On the other hand, the reactivity of gas coke is also higher, which has a favorable effect on the reaction rate.
