Abstract: A device for controlling the velocity of a particulate material conveyed by a gas flow in a duct comprises means for separating the flow into first and second streams. The first stream has a relatively high particulate material content and the second stream has a relatively low particulate material content. The flow of the second stream is restricted for example by means of a flow-constricting orifice. The effect of the device is to increase the pressure of a vessel into which particulate material is discharged from the duct, thereby reducing the velocity of the material flow.