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Show R e 0.7 d 0.6 1] O.S c 0.4 t 0.3 c 0.2 f 0.7 t 0.6 d O.S u 0.4 o OJ 0.2 120MW o lOMW n 0.1 I--..,.....~-r--~......,..-r---r-~ 11 0.1 ....... --T""---r----r---,~__, 0.7 0.8 0.9 1.0 0.7 0.8 0.9 stoichiometry of the rebum zone primary zone stoichiometry Fig 5 Reduction as a function of Fig 6 Reduction as a function of primary zone stoichiometry reburning zone stoichiometry Fig 7 shows that the reduction increased less when the natural gas/coal ratio increased within the range of our expe~iments. Overmoe /1985/ report similar results for coal as rebuming Fig. 7 ~----- Ovennoe - authors O.4~----~----~------~----~----~----~ 4 8 8 10 12 14 16 NG % Reduction of NOx as a function of the ratio NG to primary fuel, at constant stoichiometry (0,86) in the primary zone. NOx pri = 230 ppm fuel. His curve, fig 7, has a maximum at 15 % reburning fuel. This could not be verified in this authors experiments, since the maximum installed natural gas supply in Limhamn was only 16 % of the total fuel requirement. Aerodynamics A series of experiments were conducted in the isothermal model in order to optimise the position and direction of the UFI and AA nozzles. The results were verified in the input/output experiments. Fig 8 shows how an area of unburned CO existed in the centre of the boiler at bullnose level, 6. For comparison the result of the corresponding model experiment is shown. The model experiments showed that this "pillar" of unburnt could be eliminated by directing two of the AA nozzlez 20 degrees upstream in the horisontal plane. H all four AA nozzles were directed upstream, neutralisation was delayed along the walls instead. Directing the AA nozzles in a vertical direction influenced the NOx emission considerably, fig 9 7 |