FACTORS INFLUENCING THE IGNITION OF FLAMES FROM AIR FIRED SWIRL PF BURNERS RETROFITTED TO OXY-FUEL

摘要

Combustion tests were undertaken in a vertical pilot-scale furnace (1.2MWt) at the IHI test facility in Aioi, Japan, to compare the performance of an air fired burner retrofitted to oxy fired pf coal combustion with the oxy fired feed conditions established to match furnace heat transfer for the air fired case. A turn down test at a reduced load was also conducted to study the impact on flame stability and furnace performance. Experimental results include gas temperature measurements using pyrometry and inferred ignition location, flue gas composition analysis, residence time and carbon burnout. Theoretical Computational Fluid Dynamics (CFD) modelling studies using the Fluent 6.2 code were made to infer mechanisms for flame ignition changes. Previous research has identified that differences in the gas compositions of air and oxy systems influence particle ignition and also flame propagation velocity in laminar systems. The current study also suggests changes in flame aerodynamics, due to burner primary and secondary velocity differences (and hence their momentum flux) also influence flame ignition. For the oxy flame retrofit considered, the higher momentum flux of the primary stream causes the predicted ignition to be delayed and occur further distant from the burner nozzle The study was limited to experimental flames of Type-0 (that is, low swirl with no internal recirculation), and therefore future work should consider higher swirl flames (with ignition driven by internal recirculation) more common in industry.