Development of environment-friendly dual fuel pulverized coal-natural gas combustion technology for the co-firing power plant boiler: Experimental and numerical analysis

Abstract

The objective of this study was to develop and design an effective state-of-the-art dual-fuel pulverized coal (PC)-natural gas (NG) burner that incorporates fuel-air staging, flow swirling, preheating, and co-firing technologies to increase performance and minimize emissions. Experimental and numerical modeling were performed to study the effect of different operating conditions, excess air ratio, fuel staging, and NG blending. An optimal experimental design using a response surface methodology was adopted to examine the significance of the operating parameters. Analysis of variance indicates that the regression equation can correctly represent the responses (p-value < 0.0001). It is also indicated that the excess air ratio and percentage of preheated PC have significant effects on NOx emissions (p < 0.005). The optimal conditions were determined to include an excess air ratio of 1.2 and 50% PC injection into the preheating stream. Meeting these conditions, the predicted average NOx emission was 430 ± 3.1 ppm and the average measured NOx emission 436 ± 11.2 ppm, with 6% O2. Moreover, further reduction of NOx emission by up to 50% highlights the beneficial approach of NG co-firing. This design allows intensifying of recirculation and a mixture of fuels and oxidizers appropriate for improving the combustion characteristics significantly.