Nitrous oxide emissions from fossil fuel combustion

Abstract

The role of coal combustion as a significant global source of nitrous oxide (N2O) emissions was reexamined through on‐line emission measurements from six pulverized‐coal‐fired utility boilers and from laboratory and pilot‐scale combustors. The full‐scale utility boilers yielded direct N2O emission levels of less than 5 ppm. The sub‐scale combustor test data were consistent with full‐scale data, and also showed N2O emission levels not exceeding 5 ppm, although these levels increased slightly when various combustion modifications to lower NO emissions were employed. These on‐line emission measurements are very different from previously published data. The discrepancy is shown to be due to a sampling artifact by which significant quantities of N2O can be produced in sample containers which have been used in establishing the previously employed N2O data base. Consequently, we conclude that N2O emissions bear no direct relationship to NO emissions from these combustion sources, and that this direct source of N2O is negligible. Other indirect routes for the conversion of NO into N2O outside the combustor and other combustion sources not examined by this study, however, cannot be ruled out.

The heterogeneous formation of N2O over bulk condensed phases in the presence of SO2 at high humidities

“…The results obtained by Linak et al (1990) are similar to our results. These authors analyzed extracted flue gas samples using time dependent analysis of N02, NO, N20 and SOT.…”

“…Injection of water vapor at 368 K increases the initial rate and final yield by a factor of 30 to 60 compared to a dry system. These results show the importance of water for N20 production as observed in other studies (Muzio and Kramlich, 1988;Linak et al, 1990).…”

Greenhouse gas emissions from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the Mekong Delta

“…The reason the opposite phenomenon was found in these two studies might be a result of air samples for N 2 O measurement being taken without a filter in our study, but the air samples were collected with a potassium chloride-impregnated filter for removal of sulfur dioxide (SO 2 ) in Hayashi et al (2014). Because coexisting SO 2 and nitric oxide (NO) react to form N 2 O during sample storage (Muzio and Kramlich 1988;Linak et al 1990;Preto et al 2004), the N 2 O emissions calculated in our study might be overestimated, even though their contribution to global warming is negligible compared with other gas species (Fig. 5).…”

An on-line infrared spectroscopic system with a modified multipath White cell for direct measurements of N2O from NH3-SCR reaction

“…First, our gas cell coupled with IR spectroscopy is normally operated at a continuous flow of gas samples, although it was designed so as to be worked both at high pressures up to 45 psi and in vacuum as described previously. Secondly, the concentration of N 2 O emitted from fossil fuels-fired power plants was less than 5 ppm [18][19][20] and independent of the kinds of fossil fuels being used, as stated already. Based on these points regarding our continuous N 2 O measurements using the combined White cell-IR system, the pathlength is desirable to be set to 8.0 m to determine if conventional NH 3 -SCR processes play a significant role in creating substantial N 2 O formation.…”

“…The artifact would be created by the use of a grab sampling and then when allowing the samples to be awaiting for determining N 2 O concentrations, thereby giving substantial N 2 O formation in sample containers, as clearly verified by an experimental observation that large amounts of N 2 O could be produced when a gas mixture containing both NO x and SO 2 with high concentrations of thousands of ppms was passed through a weak sulfuric acid solution vessel [18], although N 2 O formation levels depended strongly not only on the SO 2 concentrations, but also on whether or not the both gases were contacted for a sufficient time. To prevent such artifact errors in grab sample measurements, the use of on-line instruments, representatively infrared (IR) spectroscopy and gas chromatography coupled with proper detection devices, for direct N 2 O measurements exhibited less than 5 ppm of N 2 O emissions even from full-scale utility boilers [18,19], which is in excellent agreement with studies of the extent of N 2 O formation for the combustion of fossil fuels in power plants [20]. This emission level is widely accepted to be a peak concentration observable at the fossil fuels-fired power plants without NH 3 -SCR deNO x processes.…”