(364a) The Influence of Fuel-Nitrogen on Soot Formation | AIChE

(364a) The Influence of Fuel-Nitrogen on Soot Formation


Kwon, H., Penn State University
Xuan, Y., Penn State University
McEnally, C. S., Yale University
Pfefferle, L. D., Yale University
In order to overcome the negative impacts related to combustion emissions, alternative fuels which mitigate soot, CO2, and other emissions are being developed. Biomass-derived fuels and ammonia (NH3)-hydrocarbon blends have emerged as possible solutions to these problems, as they have the potential to be made renewably while providing lower CO2 emissions. However, biomass and NH3 itself contains nitrogen, and the influence of nitrogen on soot formation has not been studied. Soot formation becomes relevant for biomass-derived hydrocarbons which contain nitrogen, as well as systems where NH3 is co-fired with carbon-containing fuels.

In order to close these knowledge gaps, the influence of fuel-nitrogen on soot formation was experimentally and computationally studied. To analyze the influence of fuel-nitrogen on soot formation for compounds containing carbon, the sooting tendencies of a large set (~70) of nitrogen-containing compounds were quantified using the Yield Sooting Index (YSI) and compared to sooting propensities of pure hydrocarbons and oxygenates. Sooting tendencies and decomposition pathways of select nitrogen-containing compounds were simulated using reactive molecular dynamics in order to understand the experimental trends in sooting tendencies. The influence of NH3 on soot formation was also analyzed by measuring flame characteristics and species/soot concentrations in nonpremixed laminar flames with varying ratios of NH3 and CH4 in the fuel. The NH3/CH4 flames were simulated using a detailed nitrogen-chemistry mechanism, from which important reaction pathways in these flames were examined. The results from both sets of experiments demonstrate that nitrogen has an inhibitory effect on soot formation. Nitrogen-containing hydrocarbons had an overall lower propensity to form soot than structurally analogous hydrocarbons and oxygenates. Ammonia was found to have a strong chemical effect on suppressing soot formation in CH4 flames, in addition to having a dilution and thermal effect. Soot-relevant chemical pathways which are influenced by fuel-nitrogen are discussed.