Fundamental Aspects of Coal-Water Fuel Droplet Combustion and Secondary Atomization of Coal-Water Mixtures: Final Report: Volume 2

摘要

This Final Report is issued in two volumes, covering research into the combustion of Coal Water Fuels (CWF). The present report, Volume II, covers experiments under Task 2 - ''Secondary Atomization of Coal-Water Mixtures.'' Three methods of improving spray fineness by fuel treatment were investigated - (1) the heating of the CWF under pressure to produce steam as the pressure drops during passage of the CWF through the atomizer nozzle, (2) the absorption of CO sub 2 gas in the CWF to produce a similar effect, and (3) the addition of a chemical additive which will cause microexplosions in the droplets upon heating. The effects of disruptive atomization upon CWF spray size distribution were studied using a spray test chamber equipped with a laser diffraction particle size analyzer; the data were fitted to the Rosin-Rammler particle size distribution function. The combustion characteristics of the treated CWFs were investigated in the MIT Combustion Research Facility. The spray chamber tests established that thermally-assisted atomization produced reductions both in the mean droplet size and in the mass fraction of large particles in the spray. For fuel delivery temperatures up to 100 deg C this effect is attributable to lowered fuel viscosity, while further heat of the CWF (to 150 deg C in these experiments) produces disruptive atomization. In-flame measurements and high speed cine pictures made during combustion tests provided detailed information for comparisons of treated and untreated CWF. Thermally-assisted atomization was the most effective of the methods studied for improving carbon conversion efficiency and reducing fly ash particle size. CO sub 2 and picric acid addition techniques showed substantial improvements but they were less effective. 13 refs., 15 figs., 14 tabs. (ERA citation 12:019961)