Abstract :
One of many ways of using coal as a fuel is to pulverize it into ultrafine size (200 mesh; < 75 microns); preparing dense slurries containing coal, water and small amounts of additives. This work describes an electrohydraulic (EH) approach to coal comminution where we use high energy electric sparks in water to generate shock waves with steep fronts that fracture and pulverize the coal. Under funding from DOE, Tetra corporation is conducting a series of EH coal pulverization experiments in a 4 kJ, 1 Hz, 200 ns pulse width, pulsed power facility. We have demonstrated the feasibility of the EH effect by pulverizing coal particles to below 50 microns in batch processes with energy consumption competitive with existing mechanical grinders. Measured ash and sulfur rejection rates using the EH generated shocks were fifty percent higher than in mechanical grinders. The specific energy consumption of the EH pulverizer for particle sizes below 75 /spl mu/m is lower when compared to the conventional Hardgrove ball mill crusher, but higher than the recently developed Pitt Mill crusher.
