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Show I F R F D o c N o K 7 0 / y / 1 13 IJmuiden, April 1997 -4- A F R C Spring meeting 1997 EFRF moveable block swirl generators were used to swirl the secondary and tertiary air. The combustion air was maintained at 300 °C and 40 m/s. The transport air for the primary coal was maintained at 70 °C and 20 m/s. The reburn air (also preheated to 70 °C) was used as the transport medium when coal was used as the reburn fuel. For some cases when reburning with natural gas, the reburn air was injected as by-pass air, by diverting the air into an annulus around the reburn fuel injector, in order to facilitate a direct comparison. The reburn fuel velocity could be varied in the range 10-120 m/s by interchangeable nozzles on the tip of the reburn fuel injector. Other input process variables studied during the experiments were primary zone stoichiometry XP, reburn fuel fraction Rff (and hence reburn zone stoichiometry X^), swirl number and reburn fuel type. 2.4 Facility Used For Firing Coal With Municipal Sewage Sludge The dried municipal sewage sludge and the coal were separately milled, and then fired individually or blended close to the burner. The burner furnace set-up, utilising the EFSB concept [11], allowed for burner and furnace air and fuel staging as shown in Figure 2.2. Internal fuel staging was possible with natural gas, sewage or sewage as a blend with coal. Tertiary air pipes Cooling Loops Suction Pyrometer Sewage Annulus Natural Gas or -Sewage or Blend of sewage + coal Coal Annulus \& I©) iei ie> <e> *& Figure 2.2. Furnace set-up for co-firing 2.5 Facility Used For Firing Blends Fuel staging with blended coal, required that the coals were separately milled, and fed to the burner using the setup shown in Figure 2.3. This setup also had the possibility to fire the coals without blending so that a direct comparison could be made. r < c |