Measurements and modelling of oxy-fuel coal combustion

Abstract

Oxy-fuel combustion is one of the most promising technologies to isolate efficiently and economically CO2 emissions in coal combustion for the ready carbon sequestration. The high proportions of both H2O and CO2 in the furnace have complex impacts on flame characteristics (ignition, burnout, and heat transfer), pollutant emissions (NOx, SOx, and particulate matter), and operational concerns (ash deposition, fouling/slagging). In contrast to the existing literature, this review focuses on fundamental studies on both diagnostics and modelling aspects of bench- or lab-scale oxy-fuel combustion and, particularly, gives attention to the correlations among combustion characteristics, pollutant formation, and operational ash concerns. First, the influences of temperature and species concentrations (e.g., O2, H2O) on coal ignition, volatile combustion and char burning processes, for air- and oxy-firing, are comparatively evaluated and modelled, on the basis of data from optically-accessible set-ups including flat-flame burner, drop-tube furnace, and down-fired furnace. Then, the correlations of combustion-generated particulate/NOx emissions with changes of combustion characteristics in both air and oxy-fuel firing modes are summarized. Additionally, ash deposition propensity, as well as its relation to the formation of fine particulates (i.e. PM0.2, PM1 and PM10), for both modes are overviewed. Finally, future research topics are discussed. Fundamental oxy-fuel combustion research may provide an ideal alternative for validating CFD simulations toward industrial applications.