Physico-chemical properties of low-rank coals: Thermal and demineralisation effects

Five low-rank coals, including leonardites and lignites, have been physico-chemically characterised. The effects of the carbonisation and demineralisation of some coals on mass and physical properties have also been studied. The characterisation was carried out by the chemical analyses of the coals and also by Fourier transform infrared (FT-IR) spectroscopy, gas adsorption (N2, −196 °C; CO2, 0 °C), mercury porosimetry, and density measurements. The contents of moisture, volatile matter, oxygen, carboxylic acids, and carbon–carbon double bond-containing structures are higher in leonardites than in lignites. The degree of development of surface area and microporosity is small for all coals. All samples appear to possess constrictions in micropores. The mesopore volume is significantly higher for a number of coals. The carbonisation and demineralisation of the coals produce a marked increase in the open porosity.