Relation of Air-to-Fuel and Hydrogen-to-Carbon Ratios to Flue Gases in Common Power Generation Systems

For traditional power generation fuels, the flue gas components can be viewed as continuums based on the air-to-fuel (A:F) and hydrogen-to-carbon (H:C) ratios. This paper defines those continuums for common hydrocarbon fuels (coal, natural gas and oil), in the three most common combustion systems (boilers, reciprocating engines, and gas turbines). Plotted vs. A:F in two dimensions, and then plotted vs. A:F and H:C in three dimensions, overall trends are developed for flue gas carbon dioxide and oxygen. The discussion then compares the calculation of A:F ratios in natural gas combined cycle plants with those in integrated gasification combined cycle plants. Hydrocarbon fuels with no entrained oxygen trend well in both two- and three-dimensional plots, while pure hydrogen and syngas processes do not.