CO₂‐Rich Combustion

Abstract

The atmospheric concentration of CO 2 is only around 400 ppm, and is often neglected in combustion calculations. CO 2 ‐rich combustion arises in two important contexts, namely syngas combustion and exhaust gas recirculation. Syngas is produced through the gasification of coal, biomass, petroleum (pet) coke and other opportunity fuels, and may contain between 10% and 40% CO 2 by volume. The CO 2 content in exhaust gas from fossil fuel combustion varies in the range of 5% to 15% by volume (on a wet basis), the lower end occurring in gas turbines and the higher end in case of coal combustion. In power plants involving CO 2 capture using oxy‐fuel combustion, the concentration of CO 2 in the exhaust gas can be as high as 80–85%. When this is recirculated to moderate the flame temperature in oxy‐fuel combustion, the CO 2 concentration in the combustion environment can be in the range of 50–70%. The presence of CO 2 in significant quantities in the combustion environment can alter the characteristics of the flame, such as flame length, temperature and appearance, stability, extinction, and soot formation. These aspects are discussed in this chapter, with attention primarily focused on non‐premixed flames, which are industrially important.