Nitrogen oxides emissions from the MILD combustion with the conditions of recirculation gas

Figures & data

Figure 1. Schematic diagram of the conventional flue gas recirculation and the high-temperature flue gas recirculation.

Table 1. Results of proximate and ultimate analysis for coal (unit %).

	Rank	C	H	N	S	Moisture	Volatile	Fixed C	Ash
Coal	Bituminous	74.4	4.4	1.4	0.5	5.8	30.4	55.7	8.2

Figure 2. Schematic diagram of the lab-scale combustion test system.

Figure 3. Particle size distribution of the coal.

Table 2. Summary of experimental conditions.

Item	Conditions
Baseline conditions
Fuel	Coal
Fuel injection rate	0.61 g/min
Air flow rate	6 L/min (20°C)
Excess air, %	20%
Inside diameter of the combustor	4.4 cm
Height of the combustor	100 cm
Temperature outside the combustor	950°C
Combustion test time	10 min
Conditions of simulated recirculation gas
Temperature of simulated recirculation gas	350°C
(1) Steam injection rate	0.12, 0.24, 0.36 L/min (20°C)
(2) N2 injection rate	1.5, 3 L/min (20°C)
(3) 10% CO2 in N2 balance injection rate	1.5, 3 L/min (20°C)
(4) 10% CO2 in N2 balance + 0.24 L/min steam	1.74 L/min (20°C)
(5) 10% CO2 in N2 balance + 0.24 L/min steam	3.24 L/min (20°C)

Figure 4. Concentrations of NO_x, CO, and CO₂ with time from the coal combustion with the baseline condition.

Figure 5. NO_x emissions with time from the combustion with baseline, 1.5 L/min N₂, and 3 L/min N₂ conditions.

Figure 6. NO_x emissions with time from the combustion with baseline, 1.5 L/min 10% CO₂/N₂, and 3 L/min 10% CO₂/N₂ conditions.

Figure 7. NO_x emissions with time from the combustion with baseline, 0.12 L/min, 0.24 L/min, and 0.36 L/min steam conditions.

Figure 8. NO_x emissions with time from the combustion with baseline, 1.74 L/min (10% CO₂/N₂ + steam), and 3.24 L/min (10% CO₂/N₂ + steam) conditions.

Figure 9. Percentage of NO_x emission compared to the baseline condition value.