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Show FLASHCHAIN also resolves the yields of the oxygenated gases as molecular compounds and, by difference with the total gas yield, assigns the total yield of all HC gases. An evaluation that resolves the three oxygen gas species for very rapid heating conditions appears in Figure 4. The prcxluct yields are plotted against the extent of primary devolatilization, evaluated as observed weight loss for progressively longer reaction times expressed as a fraction of the observed ultimate yields for this heating rate and pressure. The respective ultimate yields in order of increasing rank are 52.5 daf wt. % for the subbituminous (1488); 55.9 % for the Ill. #6 (1493); and 58.4 % for the Pit #8 (1451). This abscissa circumvents the need to relate the measured residence times to thermal histories, which were not measured. The predicted CO2 and H20 yields are within experimental uncertainty throughout primary devolatilzation for all three coals, and the model correctly predicts that the proportions of C~ and H20 approach 1: 1 for the lowest ranks, but fall to less than 1:2 for high-rank bituminous coals. The predicted CO yields are also within experimental uncertainty for all coals except the lli. #6 at intermediate extents of devolatilization. Additional evaluations of the predicted product distribution are reported elsewhere (Niksa 1996). APPLICA TIONS One immediate application of FLASHCHAIN is to use it as a replacement for the rudimentary rate expressions currently used in coal combustor simulators. While conceptually straightforward, this option entails extensive re-coding, and provides more detailed information on product compositions than can be used within current limitations on modeling turbulence-chemistry interactions in large-scale systems. A more expedient strategy delivers the benefits of FLASHCHAIN without the development costs of modifying the large-scale combustor code. Instead of installing FLASHCHAIN as a new submodel, we propose to use it to identify the parameter values that make the simpler rate expressions currently in use mimic the FLASHCHAIN predictions. For example, nominal devolatilization rates can always be defined from any model predictions according to the following rearrangement of a single first-order reaction rate law: dV {k} = d~ 1- V where <Ie> is the nominal devolatilization rate constant, A exp( -EJRn, S·l; and V is the sum of gas and tar yields nonnalized by the ultimate weight loss that are predicted by FLASHCHAIN. The rank dependence of nominal devolatilization rates is apparent in Figure 5 a for uniform heating at 3000 K/s to at least 1500 K at atmospheric pressure for 8 different coals whose ranks range from lignite to anthracite. Also, lengths of the curves convey the temperature intervals for complete devolatilization. Clearly, nominal devolatilzation rates of any coal type are highly 6 |