Abstract
Oxy-fuel combustion technology can capture carbon dioxide (CO2) in the large-scale and greatly lower nitrogen oxides (NOx) emission in coal-fired power plants. However, the influence of inherent minerals on NOx reduction still remains unclear and the impact of oxy-fuel combustion on the transformation of different nitrogen functional groups has yet to be fully understood. The present work aims to obtain a further understanding of the NOx reduction during oxy-fuel combustion using synthetic coals with pyrrolic or pyridinic nitrogen. Compared to pyridinic nitrogen, more of the pyrrolic nitrogen in synthetic coal was converted to NOx. The conversion ratio of nitric oxide (NO) first increased significantly with the rising oxygen content and then trended to an asymptotically constant as the oxygen (O2) content varied between 10–50%. The nitrogen dioxide (NO2) formation was roughly proportional to the oxygen content. The NO2 conversion was increased with particle size but the case of NO showed a non-monotonic variation. The catalytic effects of sodium carbonate (Na2CO3), calcium carbonate (CaCO3), and ferric oxide (Fe2O3) on the transformation of pyridinic nitrogen to NO were independent of the combustion atmosphere, while the alteration from air to the oxy-fuel combustion led to a change of mineral catalytic effect on the oxidation of pyrrolic nitrogen within the coal matrix.
Highlights
Coal combustion in utility power plants is one of the largest contributors to the anthropogenic emission of carbon dioxide (CO2 ), which brings about many environmental pollution problems, such as nitrogen oxides (NOx ), sulfur oxides (SOx ), particulate matters (PMs), mercury (Hg), and so on [1,2,3,4,5,6,7]
Regardless of the chemical form of fuel nitrogen in synthetic coal, oxy-fuel combustion leads to a certain reduction of nitric oxide (NO) relative to air condition
Most previous pilot-scale experiments indicated that compared to air combustion, the NO emission in oxy-fuel combustion could be approximately diminished by one-third to two-thirds [21,27,29,30,37], while the extent of NO
Summary
Coal combustion in utility power plants is one of the largest contributors to the anthropogenic emission of carbon dioxide (CO2 ), which brings about many environmental pollution problems, such as nitrogen oxides (NOx ), sulfur oxides (SOx ), particulate matters (PMs), mercury (Hg), and so on [1,2,3,4,5,6,7]. Ndibe et al [22] indicated that compared to the air condition, nitric oxide (NO) emission was reduced obviously during oxy-fuel combustion, while the presence of steam could further lower the formation of NO from coal nitrogen and diminish the recycled NO. Under the oxy-fuel condition with gas recirculation, the emission of NO per energy unit could be reduced by 70–75% compared to air combustion from experiments performed by Andersson et al [30]. Compared to air combustion, the influence of inherent minerals on NOx reduction in oxy-fuel combustion still remains poorly understood. Synthetic coal has not been employed to elucidate the NOx formation and its reduction mechanisms in oxy-fuel combustion yet. The present study will provide a supplementary present study will provide a supplementary information on the mechanisms of NOx formation and
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
