DEVELOPMENT OF A LASER DEVOLATILIZATION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY TECHNIQUE FOR SINGLE COAL PARTICLES

A CO2 laser Py-GC/MS system capable of identifying substantial numbers of pyrolysis products from single coal particles in the 50-150-mum ra nge is reported. Also, a specially designed two-wavelength radiation t hermometer module with integral video microscope produces reliable tem perature/time profiles of single coal particles during rapid laser hea ting. A novel microbeam footprint technique using thin quartz wafers i n combination with videomicroscopy greatly facilitates laser beam focu sing and alignment operations. Comparison of an EDB type particle levi tator with an EM grid type particle support system reveals considerabl e advantages of the EM grid approach with regard to tar collection eff iciency, particle position stability, particle visualization, and reco verability of residual char particles. However, possible cooling effec ts of the grid on highly thermoplastic particles require further study . The feasibility of simulating PCC conditions with regard to heating rates and final particle temperatures is demonstrated with complete de volatilization of a 100 mum diameter particle being observed within 10 ms. The nature and relative abundance of major pyrolysis products obs erved at typical laser heating rates (greater-than-or-equal-to 10(5) K /s) are found to be closely similar to those observed with Curie-point pyrolysis techniques at heating rates in the 10(2)-10(3) K/s range. S pherocarb particles of approximately 120 mum diameter, e.g., impregnat ed with suitable coal tar compounds, are shown to provide useful model samples for system optimization and calibration purposes.