INFLUENCE OF CROSS-LINKING ON TAR FORMATION DURING PYROLYSIS OF LOW-RANK COALS

In this paper the pyrolysis behaviour of two Spanish low-rank coal in the 275-600° C range is studied. Gases evolved from pyrolysis were analyzed by on-line Fourier transform infrared spectroscopy (EGA-FTIR) and gas chromatography and the changes in the macromolecular structure of coal by a solvent swelling technique. The studied coals cross-link very early and the differences found in their tar yields can be explained in terms of cross-linking reactions. Cross-linking of chars correlates with the evolution of CO2 and pyrolysis water and the extent of the cross-linking reactions is related to the coal's initial content of labile functional groups, namely carboxyl and hydroxyl groups. © 1990.