Effect of Gas Density on Gas Holdup in Bubble Columns

Gas density affects the gas holdup in bubble columns. Even at atmospheric pressure, different gases produce varying gas holdups. This contribution explores the causes for variations in gas holdups occurring for different gases. Differences in the bubble size distribution resulting from varying rates of bubble breakup and coalescence as well as dissimilar bubble rise velocities are the most likely causes of differences. Correlations that include a term for gas density are able to qualitatively predict the effect of changing gas density, but no correlation can consistently predict the gas holdup for multiple systems. Gases of different densities produce different bubble sizes and gas holdups. Even when sparger effects are eliminated and the primary bubble sizes are the same, this difference persists. The reasons for variations in gas holdups occurring for different gases are investigated, and the effect of gas density is discussed.