IN-SITU H-1-NMR INVESTIGATION OF PARTICLE-SIZE, MILD OXIDATION, AND HEATING REGIME EFFECTS ON PLASTICITY DEVELOPMENT DURING COAL CARBONIZATION

High-temperature in-situ H-1 NMR with a probe operating at a frequency of 100 MHz has been used to quantify the effects of particle size, mi ld oxidation, and different heating regimes on plasticity development for a low-volatile Australian bituminous coal in terms of the proporti ons of rigid and fluid material present. At the temperature of maximum fluidity, the fluid phase accounts for 35% of the hydrogen remaining, with both its concentration and mobility increasing up to this temper ature. Reducing the particle size below ca. 150 mu m suppresses plasti city through a reduction in the mobility of the fluid phase with the c oncentration of rigid material remaining constant. This effect is cons iderably more pronounced with slow heating than it is with fast heatin g (3-4 cf. 30 degrees C min(-1)). In contrast, suppressing the fluidit y by mild oxidation reduces primarily the concentration of the fluid p hase. Isothermal treatments give rise to a loss of fluidity due to red uctions in both the proportion and mobility of the fluid component. Th e in-situ measurements have confirmed that plasticity development is a reversible phenomenon provided that relatively fast quenching rates ( ca. 75 degrees C min(-1)) are used. These results are discussed in rel ation to estimating the contribution to fluidity development from the non-solvent-extractable material in coals. Heating coking coal in a tu be furnace to the temperature of maximum fluidity followed by fairly r apid cooling is shown to be a simple procedure for recovering relative ly large amounts of partially carbonized coal with the structural feat ures responsible for maximum fluidity preserved.