SUMMARYNumerical simulation of CO 2 addition effects to fuel and oxidizer streams on flame structure has been conducted with detailed chemistry in H 2 -O 2 diffusion flames of a counterflow configuration. An artificial species, which displaces added CO 2 in the fuel-and oxidizer-sides and has the same thermochemical, transport, and radiation properties to that of added CO 2 , is introduced to extract pure chemical effects in flame structure. Chemical effects due to thermal dissociation of added CO 2 causes the reduction flame temperature in addition to some thermal effects. The reason why flame temperature due to chemical effects is larger in cases of CO 2 addition to oxidizer stream is well explained though a defined characteristic strain rate. The produced CO is responsible for the reaction, CO 2 +H=CO+OH and takes its origin from chemical effects due to thermal dissociation. It is also found that the behavior of produced CO mole fraction is closely related to added CO 2 mole fraction, maximum H mole fraction and its position, and maximum flame temperature and its position.

SUMMARYA numerical study with momentum-balanced boundary conditions has been conducted to grasp the chemical effects of added CO 2 to fuel-and oxidizer-sides on flame structure and NO emission behaviour in H 2 -O 2 diffusion flames with varying flame location. A reaction mechanism is proposed to show better agreements with experimental results in CO 2 -added hydrogen flames.Oxidizer-side dilution results in significantly higher flame temperatures and NO emission. Flame location is dramatically changed due to high diffusivity of hydrogen according to variation of the composition of fuel-and oxidizer-sides. This affects flame structure and NO emission considerably especially the chemical effects of added CO 2 . The present work also displays separately thermal contribution and prompt NO emission due to the chemical effects caused by thermal dissociation of added CO 2 in NO emission behaviour. It is found that flame temperature and the flame location affect the contribution of thermal and prompt NO due to chemical effects considerably in NO emission behaviour.

Co-combustion of sludge with coal is proposed as an alternative option for sludge disposal instead of ocean dumping. Because the combustion of sludge can cause emissions of various air pollutants, it is important to understand the characteristics of sludge combustion flue gases. Especially, very few studies are found to investigate mercury emissions from the co-combustion of sludge with coal. In this study, coal and sludge samples were prepared with different mixing ratios. These samples were combusted in a bench-scale combustor, and their flue gases were analyzed. Due to higher mercury content in the sludge sample, higher mercury emissions were found with an increase in a ratio of sludge to coal. Compared to the combustion flue gas of the coal sample, higher levels of mercury oxidation were found in the combustion flue gas of the samples including sludge.

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