COALIFICATION STAGES FROM CONFINED PYROLYSIS OF AN IMMATURE HUMIC COAL

An immature humic coal (subbituminous rank) from the Mahakam delta (Ku tei basin, Kalimantan, Indonesia) was isothermally pyrolyzed in confin ed conditions at temperatures ranging from 250 to 400 degrees C (10 de grees C steps) at 700 bar pressure for 72 h. Solid, liquid and thermod esorbable phases originating from the pyrolyzates have been analyzed b y different analytical techniques. Results indicate that a 10 degrees C pyrolysis step is necessary to determine the timing and the sequence of the different transformations affecting the kerogen as well as the effluents. Four maturation/coalification stages are distinguished. St age 1 (75-80 wt.% C) occurs when modifications mainly concern the oxyg en-bearing functions of the kerogen. Stage 2 (82-85 wt.% C) is charact erized by the decrease of the aliphaticity and the primary cracking of the coal. Stage 3 (86-89 wt.% C) corresponds to the production of met hane and the condensation of aromatic rings in the solid residue.