| OCR Text |
Show 16 are similar to the uncontrolled emissions for the wood, although actual fuel S concentrations are only approximately known for the commercial units, varying from 0.03 to 0.96%. Table 4. Pollutant emission factors (% dry fuel) for open field burning, commercial biomass-fueled fluidized bed combustors (CFS), and MFC uncontrolled emissions. Field bum Wooda Rice Strawi' CO 5.54 3,22 NOx 0.20 0,28 S02 0.01 0.06 THC 0.89 0.44 aJenkins, 1994. Wood is Douglas fir slash. bJenkins and Tum, 1994. MFC, tp = 0.85 CFBc Woodd Rice strawe 0,002 0.45 0.30 0.048 0.19 0.40 0.01 0.005 0.035 0.001 0.04 0.01 cGrass and Jenkins, 1994. Includes ammonia and limestone injection. Fuels comprising urban and agricultural wood fuels with small amounts of fruit pits and nut shells. dOouglas fir stem wood. . et/J= 0.87 Conclusions Laboratory combustion results show declining NOx emission levels from biomass fuels with increasing equivalence ratio in the range 0.3 ~ tf> ~ 1 without staged combustion or secondary air addition. The results appear to be consistent with fuel NOx formation and competition for oxygen with carbon and sulfur. Reductions in NOx emission of 30 to 90% occur between equivalence ratios of 0.3 and 0.85 for the fuels tested. Although fuel NOx was not specifically determined, the majority of the NOx appears to be fuel-derived, The NOx production relative to fuel N concentration declines with increasing fuel N in a manner consistent with other nitrogen bearing fuels. The relative NOx production for biomass appears to be less than that for coal, but additional experiments under similar combustion conditions are needed to confmn this trend. S02 emissions were observed to increase with increasing equivalence ratio, suggesting competition with carbon, and possibly nitrogen, for oxygen, or homogeneous or heterogeneous reactions producing other sulfur species, not identified. Further investigation is required to determine the fate of the fuel S in the laboratory combustor. |
