A tall cylindrical vessel used for liquid-phase reactions using the sparging of a gas at the bottom to form bubbles within the liquid. The bubbles create the necessary turbulence for mixing. The surface area of the bubbles is important for mass transfer. An airlift column is a type of bubble column that has a concentric draft tube in which the bubbles rise outside the draft tube causing a liquid up-flow with the liquid flowing down the inside of the tube.