Abstract
Dielectric constants and loss factors of various coals and preheated coals were measured in the frequency range of 100kc/s-30mc/s, and following results were obtained.
1. Dielectric constant of coal decreased, with increasing C% up to d.a.f. C % of 85 percent, beyond which dielectric constant rapidly increased.
2. Dielectric constant of preheated coal slightly increased up to 600°C, beyond which increased rapidly with increase of preheating temperature.
3. Dielectric loss factor of preheated coal changed sine-curve-like against the frequency.
4. The relationship between dielectric constant and loss factor of coal heated at 650°C was in conformity with cole-cole circular arc rule.
5. The relationship between dielectric characteristics and volatile matter of preheated coal depended upon the rank of coal or heating condition.
