The electrical properties of coal slag

The inorganic constituents of coal remaining after high temperature combustion in a MHD (Magnetohydrodynamic) power plant combustor form an iron-rich, “dirty” glass whose electrical properties are important in the operation of the MHD generator. In particular, alkali “seed” (K₂CO₃) is added to enhance the conductivity of the plasma so the slag layer which coats the walls and electrodes of the generator is rich in K₂O. We present results of a systematic study of the electrical conductivity of a Rosebud coal ash with graded amounts of K₂CO₃ added. At high temperatures, the conductivity curves are smooth with many ions contributing. At lower temperatures the curves become more complex with the presence of crystalline phases in the glass.