A waste gas and theoretical air are entering a furnace at 25°C to produce flue gas at 150°C. If pure O2 rather than air is fed to the furnace, would the flue gas temperature be higher, lower or the same? Provide reasons for the answer.
The flue gas temperature be higher
Because the combustion flue gases inside the flue gas stacks are significantly hotter than the ambient outside air, they are less dense. As a result, the pressure at the bottom of the vertical column of hot flue gas is lower than the pressure at the bottom of a comparable column of outside air.