An experimental study on the stabilization limits of methane and biogas oxyflames under CO2 dilution for CCS applications
Résumé
In recent years, many environmental policies have been implemented aiming to a net zero emission energy cycle. However, given the impossibility of completely eliminating CO2 emissions from each industrial sector, methods of CO2 capture and sequestration from the flue gases (CCS) have been proposed. One of these methods is oxycombustion, which removes nitrogen in oxidizer, allowing us to obtain flue gases without N2, which will facilitate CO2 capture. Without the ballast of N2, oxyflame temperatures are higher than conventional combustion. Unfortunately, this is not suitable for many current industrial processes. Therefore, to increase the applicability of this CCS method, Recirculating Flue Gas (RFG) is implemented, inducing CO2 diluted oxycombustion operating conditions. During this study, oxyflames with different CO2 dilution rates are characterized experimentally. The flames are studied in a combustion chamber, which allows the study of the flame without the influence of the surrounding air, while emulating the combustion conditions present in boiler and furnace applications. Thanks to the optical accesses of the lab-scale facility, different laser diagnostic techniques (Particle Image Velocimetry, Planar Laser Induced Fluorescence, Spontaneous Raman Scattering) will be employed to understand the flame behavior, stability limits, in-flame temperature and species concentrations at different operating conditions. This presentation portrays the first part of this study, consisting of stability diagrams and flames characterization at different CO2 dilution rates. Two kinds of dilution are considered and gathered: RFG, when the carbon dioxide is mixed with O2 in the oxidizer, and biogas utilization, when CO2 is mixed with CH4 in the fuel. The volumetric dilution rates are represented by α and β for the oxidizer and fuel dilutions, respectively, and will vary between 0% to 50% for β and 25% to the maximum achievable for α. The different flame types observed are characterized with a combination of different measurements techniques, such as, OH* chemiluminescence for flame imaging, flue gas emissions (CO, CO2, CH4, O2, NOx), and finally temperature and thermal flux profiles throughout the combustion chamber. The results give new insights on the limits of CO2 dilution for CCS oxycombustion.