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Show ~~~====t=- 5AA -t-fto:o~------'-4UFI ~=-+--flo....------+- 3 OPA ~=+~------~~2bwme~ a) Section through boiler c) Burner paritions OFA -I-leve13 Oil burner -#~t-Ievel 2 second. air~·~t-level1 c) BurneT'. fronl:Jll view Fig. 2a) Vertikal section through the boiler. b) Burner position c) Burners, front view RESULTS, DISCUSSION Modellini In order to establish confidence in the modelling results before the model was used to optimise the reburning and additional air nozzle design and position, a series of acid/alkaline experiments were conducted, under the same conditions as the baseline trials in the boiler. The indicator dye, fenolphthalein, was mixed with the overfire air. The top limit of the area, coloured by the dye indicated neutralisation, i. e.complete mixing. The results were then compared.with the CO concentration in the furnace atmosphere, at different vertical levels and several horisontal positions. The points in the model where mixing was complete corresponded to the points in the boiler where combustion is completed, which was indicated by a minimum in the CO concentration .. A series of experiments were run, in which the concentration of the two fluids were varied to simulate varying stoichiometry, and different flow to simulate varying fuel input. It was shown that the flow and mixing pattern varied in a way that corresponded to the general experience of the project group.The experiments also gave an insight into the flow pattern in the boiler. The flames from the main burners flows downwards along the walls to the bottom of the boiler, where it turns, and flows upwards in the centre, while OFA, natural gas and the additional air flows upwards. This was later verified in the baseline experiments, fig. 3 4 |