Production of High-Temperature and High-Resistivity Semicoke from Coals of “Shubarkol Komir” JSC

Abstract

This study presented the results of an investigation into formation patterns of high-temperature specific electrical resistivity (SER) in coke produced from the coals of JSC “Shubarkol Komir” (Kazakhstan). The study also examined the impact of silica-containing surface modification and the coking temperature regime on the electrical and physico-mechanical properties of the coke. The relevance of this study determines by the need to control the distribution of electrical current and heat generation in the near-electrode zone of ore-thermal furnaces. This can be achieved by optimizing the properties of car-bon-based reducing agents.

It was established that the silica modification resulted in a 3.5- to 4.5-fold increase in specific electrical resistivity in the temperature range of 50-300 °C. At 1200°C, the increase was observed to be 1.4- to 1.5-fold. Three distinct temperature regions of resistivity change were identified: 50-400 °C (contact-degassing), 400-800 °C (intensive thermodestruction), and above 800 °C (structural ordering). It was demonstrated that the increase in SER was caused by the formation of a dielectric silica film. This was accompanied by an increase in ash content and a reduction in the bulk density of the material. A compromise between the electrical and mechanical properties of the coke was found to exist.

The obtained results expand the understanding of the mechanisms behind the formation of high-temperature conductivity in carbonaceous reducing agents. These findings maybe applied for targeted control of the electrical regime in electrothermal processes.