Coal should turn into coke or powdered carbon if it’s messed with. Coke requires enough heat to remove moisture and impurities with out consuming the coal as fuel (in blacksmithing we do this by raking coal near the firepot, but keeping it wet until it’s steamed out everything that isn’t pure coal, which is then defined as coke.)
Note: Coke has more joules of energy per weight than coal, but also dependent on if it’s lignite, bituminous or anthracite on exactly how much more that is.