OCR Text |
Show the lower-limit for volatility in their selection of coals for prepara- 7 tion in water slurries. How has this last guideline for predicting combustibility characteristics been manifest in coal-water slurry combustion testing to date? For liquid fuels, stability and ignition are critically dependent upon the degree of atomization. Coal-water slurries are an alternative liquid fuel. The Atlantic Research Corporation recently discovered that the coal-water slurry prepared from their high-volatile (40.6%) coal was much more difficult to atomize than that prepared from the lower-volatile (29.2%) one. These inferior atomization qualities translated directly into poorer combustibility qualities: with every other parameter constant (i.e., air preheat, firing rate, stoichiometry, residence time), the higher-volatile coal-water slurry had a consistently lower combustion fi ft efficiency (percent fuel carbon utilized) than the lower-volatile one. Moreover, similar operating difficulties have also been witnessed from 9 another brand-name coal-water slurry, Co-Al, in addition to those experi- 6 8 enced by the Atlantic Research Corporation, manufacturers of ARC-COAL. ' Coal-water slurry combustion tests at The Babcock & Wilcox Combustion Research Center revealed that a minimum air preheat temperature of 500°F was required for the stable ignition of a Co-Al coal-water slurry made from a high-volatile (29.4%) coal, whereas an 800°F air preheat temperature was required for the stable ignition of a Co-Al coal-water slurry 9 made from a lower-volatile (13.1%) coal. Hence, for the purpose of expeditiously promoting the utility of coal-water slurry fuels as a substitute for heavy petroleum oils, it became obvious to the author that it was imperative for the early investigations in the PSU-FCL coal-water slurry combustion research to focus on experiments that would better establish the relationships between coal volatile matter content and combustibility, the collective for ignition and burnout performance. To this end, the combustion performance characteristics of several (7, in toto) different coals of varying volatile matter content were burned in the singular PSU-FCL plane flame furnace in an effort to quantitatively establish the loss-of-ignition quality upon loss-of-volatility. 17-9 |