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chapter 5 turbulent diffusion flames - FedOA

chapter 5 turbulent diffusion flames - FedOA

NOx, mg/Nm 3 NOx, mg/Nm

NOx, mg/Nm 3 NOx, mg/Nm 3 CO, mg/Nm 3 CO, mg/Nm 3 45 40 35 30 30 25 20 20 15 15 10 5 0 160 140 120 100 80 60 40 20 0 33 33 kW 16 kW 9 kW 33 kW 16 kW 9 kW Fig. 6.4 Emission indexes (mg/Nm 3 ) for NOx and CO at 9 kW, 16 kW and 33 kW at the exhausts of commercial boilers, all measurements performed with a fixed excess air of 31% (light grey drilled premix, heavy grey metal premix). The emission of organic carbon, reported in Fig. 6.5, is also quite constant for the three loads and burner types and very low, of the order of 0.1 mg/Nm3 that is in good agreement with other investigation (Cass et al. [83, 84, 85]). In the fig. 6.5 is also reported the organic carbon captured from the condensed combustion water of the boiler that, therefore, act as a organic carbon trap. The comparison of commercial boilers exhausts with the measurements performed at the exhaust of the burners in the laboratory rig shows that organic carbon is continuously oxidized in the post-oxidation region of the boiler and is therefore reduced of one order of magnitude. Moreover a part of the organic carbon is also captured from the combustion water if condensed into the boiler. The effect of condensed combustion water on the reduction of the emission of OC is more evident comparing the emission indexes of the condensing boilers with those of standards commercial boilers using the same burners. 106

OC, mg/Nm 3 OC, mg/Nm 3 OC, mg/Nm 3 OC, mg/Nm 3 OC, mg/Nm 3 OC, mg/Nm 3 0,45 0,4 0,35 0,3 0,25 0,2 0,15 0,1 0,05 0 0,3 0,25 0,2 0,15 0,1 0,05 0 metal premix 33 kW 16 kW 9 kW drilled premix 33 kW 16 kW 9 kW Fig. 6.5 Emission indexes (mg/Nm 3 ) of organic carbon at 9 kW, 16 kW and 33 kW at the exhausts of commercial boilers, all measurements performed with a fixed excess air of 31% (light grey emission in atmosphere, heavy grey captured in combustion water). Figure 6.6 shows that in condensing boilers OC emissions are of the order of 0.1 mg/NM3, while, in standard boilers they are of the order of 0.2 mg/NM3. mg OC/Nm 3 0,30 0,25 0,20 0,15 0,10 0,05 0,00 CD 33 KW CD 16 KW CD 9 KW CM 33 KW CM 16 KW 107 CM 9 KW SM 16 KW SD 16 KW SDiff 16 KW Fig. 6.6 Emission indexes (mg/Nm 3 ) of organic carbon for several burners configuration: CD and CM are drilled and metal premix burners in condensing boilers; SM, SD and SDiff are metal premix, drilled premix and diffusive burners in standard boilers.

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