The flow characteristics in bubble column with draft tube were studied from a viewpoint of equipment dimension. Especially, the effect of length of each part such as draft tube length, upper and lower clearances, was examined. The effect of column aspect ratio (column height/column diameter) on the liquid mixing time and the effect of distance between the upper end of draft tube and the liquid surface at aeration on the liquid circulation flow rate were clarified. The relation between the circulation flow rates of liquid and gas was obtained. The results in bubble columns with contrived draft tube were shown. In the bubble column with perforated draft tube, the performances of gas-liquid mass transfer and liquid mixing were greatly improved because of the unique flow behavior. A series of studies such as combinations with packing and countercurrent bubble column, were shown. The application studies in viscous liquid and wastewater treatment were described. The effect of equipment dimension on the flow characteristics in three phase fluidized bed with draft tube was discussed.