Reactor for gas-liquid mass transfer

A reactor for gas-liquid mass transfer between a gas and a liquid or slurry, the reactor comprising:

• a tank for receiving the liquid or slurry, the tank having a wall;
• a drive shaft extending vertically in the tank and rotatable about a vertical axis;
• an upward pumping impeller for creating a flow of the liquid or slurry received in the tank generally upward and at the surface of the liquid or slurry, the upward pumping impeller being rotatable by the drive shaft and disposed in the upper part of the tank;
• an aerating apparatus disposed above the upward pumping impeller;
• wherein the aerating apparatus extends between the drive shaft and the wall of the tank at a first distance (d1) from the drive shaft and at a second distance (d2) from the wall of the tank, the aerating apparatus encircling the drive shaft at least partially,
• the aerating apparatus having a lower edge and an upper edge and, extending between the lower edge and the upper edge, an outward inclined or curved inner surface for directing at least a part of the flow over the inner surface outward from the vertical axis and over the upper edge.