3.3.3 Effect of Rising Distance on Bubble Size
Figure 12 implies the variation of the d av and bubble quantity with the rising distance of bubbles. In the range of 0-10 cm from CMGD, the d av gradually rise and the quantity of bubbles decreased with the increasement of rising distance. Because the bubbles in the water are impacted by the internal pressure of the water, and they are under less pressure as rising, resulting in a larger bubble volume. The large bubble disturbs the flow field more, attracting more small bubbles around them. Moreover, small bubbles coalesce when they are close to large bubbles. After the coalescence, the volume of large bubbles becomes larger, which will exert more influence on the surrounding flow field and other small bubbles. As a result, the bubble size magnifies while the quantity decreases with the increase of bubble rising distance. This provides a reference for the filling position of the catalyst for the gas-liquid-solid three-phase reaction in the fixed bed, that is, as close as possible to the exit of the ceramic membrane distributor, in order to avoid the influence of the coalescence of bubbles on the gas-liquid mass transfer.
FIGURE 12 Effects of rising distance on bubble sizes (d av) and quantity at a gas flow rate of 10 ml/min with 10 cm ceramic membrane