brown coal mining engineering 13 hard coal 13 coal 11 surface mining 10 opencast quarry mining 10 metallurgy 9 more ... analytical chemistry 7 history 7 combustion 6 briquetting 5 mining 5 desulphurization 4 coal energy sources 3 fluid boilers 3 geology 3 caustobiolite deposits 3 deposit geology 3 deposit prospecting 3 simulation and modelling 3 academic theses 3 biomass 2 deposits mining 2 mine fires 2 steam-gas cycles power stations 2 issues 2 power engineering 2 geologic basins 2 deep mining 2 mineral deposits 2 less ...