Zhou Junhu

Nitrous oxide formation and emission in selective non-catalytic reduction process

Pulverized coal-fired boilers are not nitrous oxide sources because of high temperature combustion. But selective non-catalytic reduction may produce N2O by NO reduction reactions. Chemical kinetics calculation and experimental research were used to find out the mechanism between N2O and N-agent species, N-agent/NO nitrogen stoichiometric ratio (NSR), reaction temperature, reaction time, etc. The results show that N2O emission decreases with increasing reaction temperature and NSR decreases when reaction time is enough. N2O concentration first increases then decreases as SNCR reactions keep on occuring. Ammonia SNCR tests indicated that N2O emission was 0–7 μmol/mol. About 8.7% of NO was transformed to N2O, and N2O emission was 27.8 μmol/mol at urea-SNCR test. Urea-SNCR is likely to bring N2O emission problem.

Kinetic modelling of homogeneous low temperature multi-pollutant oxidation by ozone: The importance of SO and HCl in predicting oxidation

A detailed kinetic model consisting of 126 reactions and 37 species modelled homogeneous low temperature multi-pollutant oxidation in flue gases by ozone. The kinetic model includes the oxidation and chlorination of key flue-gas components, as well as reactions involving SO. An important and previously unrecognized pathway of homogeneous Hg oxidation mechanism includes Hg reactions involving oxygen-containing compounds and chlorine-containing compounds. Analyses by sensitivity simulations revealed that the pathway Hg+Cl=HgCl and HgCl+Cl2=HgCl2+Cl is more significant than some of the key reactions in the kinetic mechanism proposed in the literature except Hg+NO3=HgO+NO2, which indicates the possibility to promote the Hg removal by adding HCl in the inlet stream. Studies on the effects of SO show that SO violently prevents NO consumption through the pathway SO+NO2=NO+SO2, even the net NO produced under the condition of low O3 concentration and high SO concentration.