Flow Behavior in Bubble Column with Draft Tube Installed with Perforated Plates

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The bubble column with draft tube installed with perforated plates was proposed as the reactor for the production of biodiesel from vegetable oil and superheated vapor of ethanol without catalyst. The effects of conditions of perforated plate on the flow characteristics were examined.The bubble column was made from transparent acrylic resin. The diameter was 200 mm and the height was 2000 mm. A perforated tube gas sparger was set at the bottom of the column. The draft tube with 140 mm in diameter was concentrically inserted in the column. The perforated plates were installed in the draft tube at the equal interval. The number, the hole diameter and the fraction of opening area of the perforated plate were changed. As the gas and liquid phases, air and water were used. The flow pattern was observed, and the liquid circulation flow rate and the gas holdups in the riser and downcomer were measured.By installing the perforated plate in the draft tube, the coalesced bubbles were subdivided and the liquid circulation flow rate became lower. With increasing number of the perforated plate, the gas holdup in the riser increased but that in the downcomer decreased. On the basis of energy balance, the liquid circulation flow rate was analyzed, and the empirical equation for the energy loss coefficient of perforated plate was expressed as a function of the opening fraction. From the value of rising velocity of bubble swarm in the riser, the degree of bubble subdivision by the perforated plate was evaluated. In the present experimental conditions, the degree of bubble subdivision was scarcely affected by the hole diameter and the opening fraction. It became unchanged when the number of perforated plate was more than 7, i. e. the length between plates was less than about 200 mm
日本混相流学会の論文

Flow Behavior in Bubble Column with Draft Tube Installed with Perforated Plates

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日本混相流学会 | 論文

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