This
paper compares standard gas turbine combustion chambers and
CO2-diluted oxy–fuel combustion chambers for a semiclosed
combined cycle at a preliminary design level. To this end, simple
chemical reactor networks, based on the well-stirred reactor plus
plug flow reactor scheme, are analyzed using the Cantera package and
the GRI 3.0 chemical kinetics mechanism. The focus is put on the CO
consumption process and the final CO concentration. The behavior of
this model suggests the use of the adiabatic equilibrium temperature
to characterize the composition at any station inside the chamber
and the incipient lean blow-out equilibrium temperature to fix the
well-stirred reactor volume. This model is applied to a feasible design
point of a power production cycle (combustion exit temperature 1600
K, combustion pressure 30 bar). The fuel is a natural gas with an
87% by volume CH4 content, the ASU stream is a 95% O2 gas, and the recirculated gas is an 82% CO2 gas.
The residence times required for CO burnout are approximately 30%
greater than those for air combustion for the same conditions, although
the required lengths are much closer. The residence times and lengths
would be reduced if the combustion exit temperature or the combustion
pressure of the cycle was increased.