Discharge of Bulk Solids

For simple applications it may be sufficient to let the bulk solid flow out freely from a silo or hopper. The mass flow rate to be achieved is of particular interest here, which in the case of fine-grained bulk solids depends on the behavior of the gas in the voids between the particles. Often a controlled discharge of the bulk solid is necessary, for which purpose discharge devices (feeders) are used. Discharge devices are either conveyors that have been modified to meet the requirements as discharge devices, or special devices that not only discharge the bulk solid but also stimulate it to flow within the silo. With discharge devices, it is particularly important to ensure that they remove the bulk solid over the entire discharge opening and that no stagnant zones are created. Discharge aids are used to stimulate the flow of bulk solid in the silo (e.g., when stable arches or ratholes are formed) or to improve it. The mode of operation and use of the common principles of discharge aids (pneumatic, mechanical) are described.