By means of an experimental analysis we study the granular flow in a two-dimensional silo discharged through a conveyor belt placed below the outlet. The results exhibit a saturation of the flow rate, W, with the belt velocity, v(b). Moreover, we find a dependence of the flow rate and grains velocity on the outlet size D which differs from the purely gravitational regime. To explain it, we propose an analysis based on mass conservation arguments that agrees with the experimental data when v(b) is sufficiently low. For large values of this variable, it seems to be a smooth transition between a free discharge regime (for small D) and a belt extraction regime (for large D) where the proposed model is also valid. Our analysis provides a useful connection between the flow rate and the exit geometry, a feature that may be very useful from a practical point of view. (C) 2019 Elsevier B.V. All rights reserved.