Combustion-enhancement and pollutant-control research with acoustically induced mixing. Final report

The application of acoustic energy to a pulverized-coal flame was investigated to determine its influence on NO/sub x/ generation, combustion intensity and turndown ratio. A bench-scale, research combustor utilizing plug flow and burning 5 lb/hr of Illinois No. 6C coal was tested as both a two-stage and single-staged combustor with and without acoustics applied. Sound intensities up to 149 dB at frequencies from 1100 Hz to 3000 Hz were evaluated. The experiments showed that NO/sub x/ generation was unaffected by acoustic mixing in the low first-stage stoichiometric ratio (SR/sub 1/) range of a two-staged combustor and increased up to 20% by use of acoustics in the high SR/sub 1/ range. A similar increase in NO/sub x/ with acoustics was seen in a single stage combustor operating with 5% to 20% excess air. The testing further showed that carbon burnup efficiency could be increased by 7 to 9 percentage points (in the 90 to 100% range) when acoustics were applied. Limited test data indicated that volumetric heat release and turndown ratio could be increased by a factor of 2.8. 21 figures, 3 tables.