This article proposes a phenomenological model to predict the discharge of granular solids (group D in the Geldart classification) through a valve known as the S-valve (or spitting valve), which controls the flow of solids with the injection of a gas. The model predicts the flow of solids as a function of the density of the solid (rho(s)) the friction coefficient (f(s)), the void fraction (epsilon), the gas flow (Q), the valve diameter (D-v), the pressure (P), and the spitting factor (SF). The friction coefficient, f(s), and the void fraction, epsilon, were estimated based on the surface velocity of the aeration gas using empirical relationships that were integrated into the model. The solids used were rice, lentils, and green coffee beans. The deviation from the model was +/- 3% for rice and lentil grains and +/- 2% for green coffee for a range of operation between 0.4 and 0.7 MPa. (C) 2012 Elsevier BM. All rights reserved.