A model is developed that predicts bubble dynamics and oxygen transfer in a Speece Cone. The model is based on differential mass balances for both gas and water and requires a knowledge of cone dimensions, water flow rate, depth to the cone, and initial bubble diameter produced by the oxygen diffuser. The model calculates the oxygen transfer, nitrogen stripping, and gas-phase holdup within the cone. Experimental data for a Speece Cone have not been published; however, a modified version of the model is tested using data obtained from a hydrodynamically similar full-lift hypolimnetic aerator with good results. This process model, when coupled with a suitable cost model, should prove useful in the preliminary design and economic optimization of Speece Cone oxygenators.