OCR Text |
Show and mineral matter (ash), and the lower the atomic H/C ratio, the greater the tendency for the combustion of that fuel to result in higher nitrogen oxides [NOX], sulfur oxides [SOX], inorganic particulates [ROX], and smoke pollution, respectively. Table II has been constructed from the data in Table I and the aforementioned "rules of thumb" and shows comparisons between convetional solid boiler fuel [bituminous coal] and the various alternative solid fuels. The scoreboard data given in Table II only provide a qualitative analysis of the similarities and differences among pulverized solid fuels. As such, Table II exposes and justifies the vital need for a quantitative data base to be established on the combustion performance characteristics of pulverized fuels, in order to replace the letters in Table II with numbers. First results have already been published on the comprehensive and systematic combustion research program, underway at The Pennsylvania State University Fuels and Combustion Laboratory and under the direction of the author, studying combustion phenomena and how the compositional properties of a wide spectrum of solid, liquid, gaseous, and multiphase fuels and combustor operating conditions and configurations determine physicochemical combustion behavior. The purpose of this paper is to present the first comprehensive results of a parallel program directed toward the characterization of the combustion properties of coal-water slurry fuels as determined by the parent coal precursor. Table III represents a "scoreboard" of known qualitative combustion performance data for coal slurry fuels compared to heavy oil and the parent coal. In order to discover why coal-water slurries have performed the way they have in preliminary combustion tests to date requires a parametric program designed to study the following: the effect of coal rank, coal particle size, coal-water loading, preheating, recirculation, first (and overall) stage(d) combustion stoichiometries, and timing of secondary-staged-combustion air injection on such flame properties as temperature, radiant heat transfer, products of combustion, length (equal to the sum of ignition, reaction, and burnout times), thermal and combustion efficiencies, and derating potential. With regard to coal properties, 4 it has now become apparent from recent publications by vendors that particle size and coal-water loading are, for all pratical purposes, somewhat fixed by whatever proprietary fuel preparation technique is 17-5 |