Gas-liquid multi-phase processes are widely used for processes that require reactions. To increase productivity in these reactions one potential method is to increase the gas flow rate into the vessel. This means that it is important to understand how these reactors perform at high gas flow rates, which can create problems such as zones within the vessel. This paper investigates the mixing performance and the mass transfer in dual agitated systems at high gas flow rates. Two configurations have been compared a 6 blade disk turbine (Rushton turbine) below either a 6 Mixed flow Up-pumping or down-pumping agitator. Zoning has been identified by Electrical Resistance Tomography which affects the mixing time within the vessel, with increasing agitation rate potentially increasing the mixing times at high gas flow rates. At these high gas flow rates the zoning also affects the mass transfer meaning that it is not constant within the whole vessel. However, dividing the vessel into the key zones allows the mass transfer rate to be predicted with a single equation. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.