Temperature dependence of the electrical conductivity of sintered coal

Conclusions

• 1. Absorbed water increases the electrical conductivity of coal.

• 2. Water desorption is completed in the range 200 °–250 ° C, the curve 1g ϱ =f(1/T) is reversible for dried coal heated to not more than 400 ° C, and the conductivity is ionic.

• 3. Between 420 ° and 450 ° C a structural transformation occurs due to the breaking off of the side bonds of the polymer lattice, with the result that the conductivity gains an electronic component and the resistance falls irreversibly.

• 4. In dried coal the resistance along the stratification is roughly 1% that at right angles to the stratification, while the 1g ϱ =f(1/T) curve retains the same shape in either case.

• 5. The activation energy of the electrons is 2–3 eV, while that of the ions is 0.3–0.6 eV (for movement at right angles to the stratification), so that the ionic component of the conductivity predominates at temperature below 400 ° C.