Abstract: Characterization of Thermogenic Gases from Polish Bituminous Coals by Hydrous Pyrolysis and Stable Isotopes

KOTARBA, MACIEJ J., and MICHAEL D. LEWAN

Hydrocarbon gases (mainly methane) and carbon dioxide are commonly associated with bituminous coals in the Upper Silesian (USCB), Lower Silesian (LSCB) and Lublin (LCB) coal basins, Poland. Ignition of the hydrocarbon gases in USCB, LSCB and LCB, and outbursts of rocks and carbon dioxide in LSCB cause serious life-threatening situations and render some mining operation uneconomical.

Hydrous pyrolysis was used in this study to generate thermogenic gas from the coals because it better simulates natural coalification process than both closed-system and open-system anhydrous pyrolysis. All of hydrous pyrolysis experiments were conducted at 360 degreesC for 72-hour duration. The experimental results are related to maceral composition, vitrinite reflectance, elemental composition (atomic ratios H/C and O/C), and Rock Eval Tmax values. Vitrinite reflectance values vary from 0.59 to 1.14% for 14 natural coals, and from 1.68 to 1.85% for the same coals after hydrous pyrolysis, respectively.

In addition to providing constrains on molecular and isotopic [delta¹³C(CH₄), deltaD(CH₄), delta¹³C(C₂H₆), delta¹³C(C₃H₈) and delta¹³C(CO₂)] composition of thermogenic gases from these experiments were quantitatively collected to provide amounts of thermogenic gas generated per unit mass of coal. Stable isotope ratios for gases expelled during hydrous pyrolysis vary within the following ranges: delta¹³C(CH₄) from -36.6 to -33.5 o/oo, deltaD(CH₄) from -319 to -304 o/oo, delta¹³C(C₂H₆) -27.0 to -25.2 o/oo, delta¹³C(C₃H₈) from -26.1 to -23.9 o/oo and delta¹³C(CO₂) from -20.5 to 4.9 o/oo.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria