| OCR Text |
Show Figure 5. Acid/Alkali model of the precessing jet (PJ) flame with 3 0 % of fuel introduced through the center body jet (10.6% excess air). Therefore, the coal firing element was designed under the constraints of the existing coal firing system. Coal firing with the new burner was compared with the operation of the original coal burner design. Figure 6 compares the flame length and excess air relationships for the new and old burners. The similarity implied that the new burner firing coal would operate in a similar manner to the original coal burner, however, kiln shutdowns will not be required in the event of 1 0 0 % coal firing. The precessing jet nozzle firing gas only was modeled next to investigate the effect of cooling air, and then to observe the effect of the precessing gas and center body gas split. First, and perhaps most importantly, the modeling demonstrated that no adverse aerodynamics existed as if present they could seriously disturb flame patterns upsetting kiln operation (13). Secondly, it confirmed that the flame shape would be controlled by adjusting the center body to precessing jet gas ratio, while adjusting the cooling air flow is unlikely to have a great affect on flame shape at lower air flows. Modeling techniques for precessing jets have yet to be developed and validated. Therefore, cofiring coal and gas with the precessing nozzle was not carried out. 10 |
