PREDICTING THE DEVOLATILIZATION BEHAVIOR OF ANY COAL FROM ITS ULTIMATE ANALYSIS

FLASHCHAIN has been developed to predict yields and product characteri stics from any coal for any operating conditions. This evaluation demo nstrates the model's utility for the usual situation where the ultimat e analysis is the only sample-specific information available. It also identifies the key reaction centers in coal as its structural componen ts called labile bridges. Their elemental compositions are grossly dif ferent than the analogous whole-coal properties, showing much stronger rank dependences and a much higher degree of sample-to-sample variabi lity. In light of these findings, it is inconceiveable that bridge con version rates are rank-independent. Parameters in the rate law for bri dge conversion in FLASHCHAIN are now explicitly related to the element al compositions of bridges. The (O/C)(B) ratios are the best regressio n variable for the rate constants because oxygen is the most effective promoter of pyrolytic decompositions. The (O/H)(B) rates are best for the selectivity coefficient between scission and condensation into ch ar links because oxygen promotes crosslinking but hydrogen addition to broken bridge fragments stabilizes them. These extensions are evaluat ed in comparisons against a database of 27 coals that span all ranks f rom lignite to anthracite, for heating rates from 5 to 5000 K/s, ultim ate temperatures to 1300 K, and pressures from vacuum to 70 MPa. In fo ur out of five cases, predicted total and tar yields are within experi mental uncertainties. The model is also used to rigorously define nomi nal devolatilization rates for diverse coal types and broad ranges of operating conditions. Nominal rates have very low activation energies, proving that heat and mass transport resistances are not responsible for the low values because this theory is completely free of these con siderations. Whereas nominal rates are rather insensitive to coal type variations and independent of pressure, they vary in proportion to ch anges in heating rate.