The present invention pertains to a system of unloading bulk material that comprises at least a silo for receiving a bulk load discharged from a load transport means; and at least a feeder to feed the load from the silo to a conveyor belt. The system comprises a flow control means that regulates the operating parameters of the feeder to make sure that an estimated calibrated flow rate corresponds to a desired flow rate, where the estimated calibrated flow rate is obtained based on a calibration factor calculated by comparing an estimated flow based on an operating parameter of the feeder with a real flow measured downstream of the silo.