Pressurised steam drying of Australian low-rank coals: Part 2. Shrinkage and physical properties of steam dried coals, preparation of dried coals with very high porosity

The shrinkage of brown coal during high pressure steam drying and the physical structure of the product have been investigated by mercury porosimetry, CO2 surface area analysis and transmission electron microscopy (TEM). The porosity of the coal can be tailored by controlling the temperature-time profile of the steam drying and samples with very high porosity can be obtained when drying is carried out under mild conditions. These examples also showed high surface area values as determined from CO2 adsorption measurements. The TEM measurements showed no evidence for tar mobilisation other than at 254°C, the highest temperature used. A simple conceptual model has been proposed to explain these findings.