The literature proposal of using the Harcourt and Esson approach for determining the activation energy as a function of the conversion front a single non-isothermal experiment has been reanalyzed. It has been shown that the kinetic equation resulting from this approach was not properly derived. It has been demonstrated that the use of this approach necessarily leads to an apparent linear increase of the activation energy with the temperature independently that the activation energy would be either constant or a function of the conversion.