Ammonia/coal binary fuel gasification-combustion technology: Experimental study of optimal parameters for assisting denitrification and strengthening combustion

• Optimal parameters for NH 3 /coal gasification-combustion technology was explored. • Co-firing NH 3 with primary air was more advantages in NO x controlling. • Optimal gasification temperature range of 900 °C − 1100 °C was identified. • Reasonable air distribution method with λ 3 of 0.5 balanced NO x emissions and fuel burnout. The gasification-combustion technology has proven to be significant potential in assisting denitrification and strengthening combustion for ammonia (NH 3 )/coal binary fuels. However, previous studies have been limited to laboratory-scale, self-sustaining test rigs, restricting comprehensive investigations. Therefore, an electrically heated dual-temperature-zone gasification-combustion experimental platform was used in this study to systematically explore the effects of co-firing mode, gasification temperature, combustion temperature, and air distribution methods on fuel nitrogen (Fuel-N) transformation, gaseous fuel concentration distribution, nitrogen oxides (NO x ) emissions, and combustion characteristics during NH 3 /coal gasification-combustion. First, under 20 % NH 3 co-firing with primary air (PA_NH 3 ) mode, NH 3 conversion and Fuel-N to nitrogen (N 2 ) conversion in gasifier exceed 80 %, while NO x conversion rate remains below 0.1 %, which is favorable for fuel denitrification and controls NO x emissions. Besides, the concentration of highly reactive gaseous fuels is over 12 %, which strengthens homogeneous combustion intensity and promotes NH 3 /coal burnout. Second, as gasification temperature rises from 900 °C to 1100 °C, NH 3 and N 2 conversion rates increase without NO x detected at gasifier outlet, which improves the denitrification performance and reduces NO x emissions. Meanwhile, the conversion of NH 3 /coal to highly reactive gaseous fuels is promoted. However, above 1100 °C, the conversion of Fuel-N to NO x and hydrogen cyanide (HCN) are promoted, deteriorating NO x emissions. Furthermore, increasing combustion temperature improves the burnout performance of NH 3 /coal, but is harmful for NO x control. Finally, as tertiary air ratio (λ 3 ) increases, NO x conversion is suppressed in the gasifier. However, further increase reduces NH 3 and coal conversions, increasing the nitrogen source for NO x formation in down-fired combustor (DFC), thereby exacerbating NO x emissions. Overall, in PA_NH 3 mode, with λ 3 assigning to 0.5 and gasification and combustion temperatures setting to 1100 °C and 1200 °C, respectively, the gasification-combustion technology demonstrates high efficiency in assisting denitrification and strengthening combustion for NH 3 /coal binary fuel. At CR = 20 %, NO x emissions are similar with those of pure coal condition, while promoting coal burnout. This study optimizes operating parameters for NH 3 /coal binary fuel gasification-combustion technology, providing valuable data and theoretical support for its development.