The effect of microwave radiation on coal grindability

Coals of various ranks were exposed to microwave radiation to quantify the effect on grindability. Reductions of up to 50% of the relative grindability of the coals were reported after 5 min microwave exposure. These are believed to be a combination of fracture mechanisms, inherent moisture within the coal structure changing phase under considerable pressure and differential expansion by gangue mineral components. The overall effect of microwave radiation on the coal calorific value was minimal and compares equally to conventional drying techniques. Future work will include scaling up to pilot plant level (50–100 kg/h) to allow an accurate techno-economic assessment of the process.