The present invention provides a method for emptying a reactor containing at least one bed of spent catalyst particles, wherein the reactor comprises at least one dump tube that opens into the reactor. The method comprises the steps of: (a) causing a portion of the bed of spent catalyst particles to flow out of the reactor via the dump tube; and (b) expelling the remainder of the spent catalyst particles from the reactor by driving the remainder of the spent catalyst particles toward the opening of the dump tube using a removable device comprising at least one rotary brush fixed to the end of an articulated arm introduced into the reactor via the dump tube.