Numerical investigation of oxy-coal combustion to evaluate burner and combustor design concepts

Significant progress has been made in both experimental investigations and numerical modelling of oxy-fuel combustion for CO2 capture purposes at the CANMET Vertical Combustor Research Facility. Detailed inflame measurements have revealed insights on flow field development and pollutant formation characteristics over a wide range of operating conditions using natural gas and coals. A numeral modelling capability has also been developed in parallel and validated by in-flame data. This study marks the first use by CANMET of this numerical modelling expertise to develop design ideas before expensive and time consuming experimental work is done. Its focus is on evaluating burner and combustor design concepts for oxy-coal combustion when air is substituted for oxygen in the recycled flue gas (RFG) mode. Model results indicate that a new burner design approach can potentially reduce NOx at furnace exit by over 70% with respect to the existing design, while providing significant improvements in overall flame characteristics. Finally, the numerical study produces quantitative evidence in support of enlarging the present combustor to an inner diameter of one meter in order to minimize wall effects, which become important when trying to expand the flame volume so as to improve oxygen management within the flame.