Researchers studied how to reduce NOx emissions in a large oxy-coal combustion boiler. They found that staged oxy-fuel combustion can significantly decrease NOx formation. By using fuel staged combustion and fuel-oxygen two-way staged combustion, NOx emissions can be reduced by 16% and 22-30% respectively. Increasing the equivalent ratio in the burner zone further reduces NOx emissions. The most effective method, fuel-oxygen two-way staged combustion, can lower NOx emissions by up to 30%, resulting in a 69% reduction compared to air-fuel combustion. This study provides valuable insights for reducing NOx emissions in oxy-fuel combustion systems.