Influence of operating pressure on combustion and heat transfer in pressurized oxy-fuel combustion evaluated by numerical modeling

Abstract

Pressurized oxy-fuel combustion (POFC) is an advanced-generation energy plant system that is used to capture and store carbon and can realize a high-efficiency generation cycle with increased heat transfer and minimized efficiency penalty. In this study, we conducted a numerical investigation to characterize the heat transfer, combustion reaction, and NOx emissions of a 0.1 MWth POFC system. In addition, the weighted-sum-of-gray-gases (WSGG) model was applied in the POFC conditions to precisely evaluate the radiative heat transfer based on a comparative analysis of various WSGG models. Both the measured and calculated results revealed that the temperature, including its peak value, decreased with the increasing pressure. Moreover, the average total heat recovery rate increased by approximately 0.2% upon increasing the pressure by 2 bar, and the proportion of the radiative heat transfer rate increased. Furthermore, the combustion reactions containing the O, H, and OH radicals were promoted with the increasing operating pressure, exhibiting a high peak value in a wide area. Consequently, the net reaction rates of the reactions involving HO2 and H2O2 increased with the pressure. Overall, NO was produced in the initial section of the oxy-flame, beyond which the oxidation reaction of NO with HO2 occurred to yield NO2, and the increasing pressure further promoted these reactions.