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