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Show 00' 2.(t 1.8 1.6 1..4 l.l 1.0 0 .• 0.6 0.4 0.2 boiler Fig 8 ~C~Pleted IDlXlng . ? v ~~ model ! I . J~ CO profile across the boiler furnace, at the bullnose level. Comparison with mixing in model experiment NOx ppm 8o-11{) 100-120 110-130 120-140 C I N fLYU~ 15- 20~ 10-12'" <'O .6~ Fig 9 NOx and carbon in flyash for different AA and UFI directions in a vertical plane 8 The numbers in the boxes in fig 9 are the volume of the reburning zone, from the model experiments, as a percentage of the available volume between the OFA ports and the bullnose. The figure shows that the UFI nozzles influence the mixing very little. The reason is that the momentum of the gas jets is very small in comparison to the air jet momentum. The reason why the residual carbon in the flyash decreases as the direction of the AA nozzles change from upward to downward is probably that char particles, not completely burned out, pass the reburning zone. The larger final burnout zone then give the particle longer residence times in the far right figure. The best combination of low NOx emission and more complete burnout would probably be achieved if both the AA and UFI nozzles pointed upwards, or even installed at a higher level in the boiler. This could not be tried in the boiler, however. Okigami /1985/ reported experiments, both in a laboratory furnace with a maximum thermal load of 1.5 MW, and in two production units. Fig 10 and 11 show comparisons of the results with the reburning experiment at full load in Limhamn. The opposite fired boiler emits less NOs than the 3DO opposite finq froDt finDI! -• 0 : AuIIrIiI\en COIf • LimblmD 0 ; South Atria., coal - loS MW lab uDil ~ Q 2DO .3 .. --: : ~-- .. li ! I 100 S Z 0 1 0, ~/Qr1 In ,- .. f"') Fig 10 NOx emissions from boilers with different aerodynamics Function of 02 in flue gas ~ lIDO Fig 11 NOx emissions from boilers with different aerodynamics Function of primary zone stoichiometry front fired, probably due to superior mixing. The point representing the laboratory furnace , in which a nearly ideal mixing was maintained, supports this conclusion. The NOx emission during the Limhamn experiment agrees closely with Okigamis laboratory experiment. This indicates that the mixing in the Limhamn boiler was very satisfactory. Chen /1986/.studied different injection methods in a pilot plant, fig 12 |