EFFECT OF DRAFT TUBE POSITION ON THE HYDRODYNAMICS OF A DRAFT TUBE SLURRY BUBBLE-COLUMN

Two- and three-phase hydrodynamic studies were conducted in an air lif t bubble column with an internal loop. The bubble column had a conical distributor at the bottom, through which the gas was sparged, creatin g a liquid or slurry circulation from the draft tube to the annular re gion. The axial position of the draft tube was varied with respect to the conical section. The experiments were performed with the air-water system at ambient conditions, using siliceous sand as the solid phase . When the bottom of the draft tube was located precisely at the trans ition between the conical and cylindrical regions, no liquid circulati on was observed. When the draft tube was located in a lower position, liquid circulation started and its magnitude increased as the draft tu be was further lowered inside the conical region. The results presente d indicate that the hydrodynamic behaviour of these systems can be eff ectively controlled by varying the axial position of the draft tube.