A flotation model is used to calculate the flotation rate constants of methylated quartz particles as a function of particle diameter in the Jameson cell downcomer. This model includes the frequency of collisions between particles and bubbles as well as their efficiencies of collision, attachment, and stability. Especially, the turbulent energy dissipation of the downcomer is derived on the base of phase interaction of a two-phase fluid model to avoid the complex and costly measurements of the fluctuations of the turbulent fluid velocities. The flotation rate constants calculated with the model produced the characteristic shape of the flotation rate constant versus particle size curve, with a maximum appearing at intermediate particle size. The low flotation rate constants of fine and coarse particles can be attributed to the low collision efficiency and low stability efficiency, respectively. The values of the calculated flotation rate constants are in good agreement with the experimental data. However, the calculated flotation rate constant is slightly lower than the experimental data Which may result from some ignored interactions when the turbulent energy dissipation is derived. Therefore, more work is needed to identify the effects of turbulence in the Jameson cell downcomer. (C) 2017 Elsevier B.V. All rights reserved.