Assisting denitrification and strengthening combustion by using ammonia/coal binary fuel gasification-combustion: Effects of injecting position and air distribution

The direct co-firing of ammonia (NH 3 ) with coal is an effective approach for reducing carbon emissions from coal-fired plants. However, the limitations of NH 3 combustion, such as its high ignition energy requirement and high NO x emissions, restrict its large-scale co-combustion in coal-fired units. In this study, a self-sustaining gasification–combustion experimental system was employed, and its denitrification performance and combustion strengthening capability for NH 3 /coal binary fuel under different NH 3 injection positions and air distribution methods were evaluated. The results of co-firing 20 % NH 3 in the gasifier revealed that its operating temperature can be flexibly controlled within the optimal reaction temperature window of SNCR by adjusting the primary air ratio (λ 1 ). Increasing λ 1 was beneficial for NH 3 and coal conversion and denitrification in the gasifier; at λ 1 = 0.53, the conversion rate of NH 3 and N 2 reached 86.37 % and 83.59 %, respectively, with no NO x being detected at the gasifier outlet. Furthermore, increasing λ 1 promoted the development of gasified char pore structure , thereby improving reactivity. After entering the down-fired combustor (DFC), increasing λ 1 promoted NH 3 and coal burnout and effectively controlled NO x emissions, reaching a level similar with that of pure coal under λ 1 = 0.53. Co-firing 20 % NH 3 in the DFC also demonstrated that the introduction of inner secondary air was conducive to char burnout , however, increased NH 3 slip. The outer secondary air promoted NH 3 combustion, however, exacerbated NO x emissions and inhibited gasified char combustion . The uniform air distribution method balanced the combustion of NH 3 and gasified char, and effectively controlled NO x emissions. When the same air distribution method was used, co-firing NH 3 in the gasifier was more favourable for NO x control, whereas co-firing NH 3 in the DFC benefited coal burnout. This study provides innovative ideas and serves as a reference for developing enhanced combustion and low NO x emission technologies for large-scale NH 3 co-firing in coal-fired units. • NH 3 /coal gasification-combustion studies conducted in a self-sustaining furnace. • Effects of primary air ratio were explored during NH 3 co-firing in gasifier. • Effects of secondary air distribution were studied during NH 3 co-firing in DFC. • NO x emissions and fuel burnout of different NH 3 injection position were compared.