Abstract
To give a role of immobilizing carrier to a draft tube, a packed double perforated draft tube was proposed and the liquid mixing and gas-liquid mass transfer of a bubble column with this type of draft tube were examined. The packed double perforated draft tube consisted of two different-diameter perforated tubes and the space between two tubes was filled with particles. Under various combinations of inside and outside diameters of draft tubes and particle diameter, the flow pattern was observed and the liquid mixing time, gas holdup and volumetric mass transfer coefficient were measured.
When the packed double perforated draft tube was used, a part of gas and liquid flowed radially through the particle layer and large bubbles were then subdivided into fine ones. For the liquid mixing time, gas holdup and volumetric coefficient, the diameters of particle and draft tube had optimum values. From comparison of the flow characteristics of the proposed type with those of conventional bubble columns, it was found that the packed double perforated draft tube was effective for the improvement of liquid mixing and gas-liquid mass transfer, especially when the bubble size was relatively large.
