OCR Text |
Show It was previously mentioned that the air flow from each burner was within + 8.5% and - 6.1%. Evaluation of the individual readings indicated severe maldistribution in each burner throat Fig. 6 I Polar diagrams. In addition, extremely high swirl was detected which reversed when the mod~l 'pulsed'. Both these characteristics were totally unacceptable to the burner type fitted and almost certainly to any design of burner. The solution is illustrated in Fig. 7 F and resulted in fully stable flow regimes, air distribution within ± 2% of the mean Fig. 9 F, good distribution in each burner throat and zero or minimum induced swirl at each burner exit Fig. 6 F. The net result after implementation on site is four even flames and the capability to operate at low excess air levels, NOx and particulate emission have also dropped proportionally. Case 2: A Steam Boiler fitted with three large capacity gas fired burners. This boiler was of the type that can be utilised in the semi waste-heat mode or fired directly when waste-heat exhaust gases were not available. The plant is relatively new and designed with the aid of model testing at the initial concept. The basic layout of the FD system was however fixed due to site plot restrictions Fig. 10. - 14 - |