| OCR Text |
Show decreasing the excess air, increasing the oxygenation of the fuel, decreasing the furnace exit temperature, and increasing the fuel volatility will, in combination, cause a reduction in NOx emissions. Alternatively: NO", bMMBtu = 0.76(FN) -1 . 17(VIFC) + 4.45(02E) + 0.0007(FET) [7] where FN is the nitrogen content of the fuel expressed in Ib/l06 Btu, V!FC is the volatile/fixed carbon ratio from the proximate analysis, 02E is the oxygen content of the flue gas at the economizer exit expressed as a decimal, and FET is the furnace exit temperature (F). The r for this equation is 0.82. The factors shown above all indicate that cofiring and trifiring should reduce NOx emissions by impacting fuel nitrogen content, fuel volatility, furnace exit temperature, and the inherent oxygen content of the fuel blend. This influence is shown in Figure 5. Note that the impact of wood waste cofiring is linear with respect to eastern or interior province bituminous coal. The impact on western coal is less dramatic, and appears to be optimized when the cofiring level is in the 15 to 20 percent biofuel range. It should be cautioned, however, that these are the results of parametric tests, and that ~xtensive additional tests may be required to optimize the system and maximize the NOx reductions. ::J m ~ 2.500 2.000 ~ 1.500 -E. Ii c o ~ to ~ 1.000 )( o z 0.500 0.000 Figure 5. Nox Emissions as a Function of Percent Wood in Fuel Blend y = -O.0266x + 2.0713 ~ -Eastern C-oal line ! _ . R2 = 0.7175 .. - • ~ - ~-- t I - Western Coal lIn~ • y = 0.0019x2 - 0.0479x + 1.4323 R2 = 0.6247 o 2 4 6 8 10 12 14 16 18 20 Percent Wood in Blend 14 |
