EXPERIMENTAL ANALYSIS OF CO2-DILUTED GAS FLAMES FOR CARBON CAPTURE.

Current extreme weather events are evidence of the global climate change and its effects on the environment. Although natural gas is a "greener" fuel compared to solid fuels, its continuous uncontrolled use will increase further the atmospheric CO2 emissions above sustainable levels. Natural gas fired power plants equipped with a carbon capture plant can serve as a short, and medium, term solution to mitigate global warming. Several research studies have shown that post-combustion capture technology is a readily available option to reduce drastically the CO2 emissions. However, its associated energy demand for separating CO2 from the other exhaust gases is high and needs to be reduced. Therefore, recirculating part of the exhaust gases to the inlet of gas turbine combustors increases significantly the exit CO2 concentration which is the driving force of the capture plant. This fundamental study focuses on the implications of the addition of CO2 on fuel-lean natural gas non-premixed flames. The thermal and chemical effects of adding CO2 in the air stream on the flame chemistry, properties, stability and the formation of pollutant emissions represent the main aim of the present study. Two experimental campaigns were performed in this study and in-flame, post-flame and exit measurements of major and minor combustion species and the flame temperature are performed utilising an in-house built combustion chamber. Experimental results concluded that CO2 has a considerable impact on the combustion process even at relatively low dilution levels. However, the effects of the dilution can be controlled in a beneficial way for the efficiency of the combustion systems. Furthermore, the assessment of the performance of a 1D numerical model on predicting the implications of the addition of CO2 on the flame chemistry was part of this study. The numerical results concluded that robust complex combustion models are needed to examine CO2-diluted combustion systems and it is evident that detailed chemical reaction mechanisms are as necessary as the inclusion of the interaction between turbulence and chemistry.