A 0.5 MW oxy-fuel boiler was created to capture CO2 from exhaust gas using natural gas as fuel. The researchers studied oxy-fuel combustion without flue gas recirculation, finding that a flame with 32% oxygen concentration stabilized the combustion. They observed flame delay at partial load for oxy-natural-gas FGR combustion but not for other modes. In oxy-fuel combustion, the temperature near the wall remained high due to gas radiation effects. When oxy-fuel and FGR combustion were used in industrial boilers, over 90% of CO2 was captured, meeting exhaust gas regulations.