INTERLABORATORY COMPARISONS OF PETROGRAPHY OF LIQUEFACTION RESIDUES FROM 3 ARGONNE PREMIUM COALS

Three Argonne Premium coal samples, the Beulah-Zap lignite (North Dako ta), the high Volatile A bituminous Stockton (West Virginia), and the low volatile Pocahontas No. 3 (Virginia), were ground to three initial sizes: -20 mesh, -100 mesh, and ''micronized''. The samples were each subjected to liquefaction at 673 K for 30 min at a 2:1 tetralin:coal ratio and in an H-2, atmosphere at 13.79 MPa (similar to 2000 psi). Po lished pellets of the unconverted residues were circulated to three la boratories for a study designed to determine, albeit on a limited scal e, the interlaboratory consistency in constituent identification and t he problem areas in maceral/neo-maceral/mineral recognition. Within br oad categories, the agreement for the Beulah-Zap and Pocahontas No. 3 residues is good. The high volatile A bituminous Stockton coal was the most plastic and most altered, resulting in a residue lending itself to more subjective interpretations. The biggest discrepancy between th e laboratories is in the distinction of granular residue and mineral m atter and in the transitions between ''partially reacted macerals'' an d ''vitroplast'' and between ''vitroplast'' and ''granular residue''. The initial size of the feed coal appears to influence the recognition of material in the residue.