THE INFLUENCE OF MICROWAVE DRYING ON PHYSICOCHEMICAL PROPERTIES OF LIUSHUHE OIL SHALE; pp. 29–41

In this paper, microwave drying of Liushuhe oil shale was studied and compared with conventional drying process. Oil shale was treated in a microwave oven at four different microwave energy levels. The drying trial showed that the drying rate of microwave drying was much higher than that of conventional hot air drying. Attention has been given to the influence of microwave treatment on the physicochemical properties of oil shale. Samples dried at 550 W for 15 min (MD3) were chosen as the representative ones for microwave drying. The grindability of oil shale samples was characterized by Hardgroove grindability index (HGI). It was found that significant increases in oil shale grindability could be achieved after exposure to microwave energy. The pore structure of raw oil shale (OS) and dried samples (CD and MD3) was measured by the method of low-temperature adsorption of nitrogen. Specific surface area was calculated based on Brunauer–Emmett–Teller (BET) equation, and pore size distribution was calculated by Barrette–Joynere–Halenda (BJH) method. The results showed that the specific surface area and specific pore volume of CD and MD3 increased considerably, and microwave drying led to the formation of mesopores. Fourier transform infra­red (FTIR) spectra indicated that microwave drying had no significant effect on the chemical property of oil shale.