An apparatus includes at least one electron beam generator for generating accelerated electrons with which bulk material particles are impingeable during free fall. The electron beam generator has an annular design in which the electrons are emitted and accelerated by an annular cathode. The electrons exit from an electron outlet window in the direction of the ring axis. The annular electron beam generator is arranged in such a way that the ring axis of the electron beam generator is oriented perpendicular to, or at an angle of up to 45° from the horizontal. The apparatus may further include a device for separating bulk material particles arranged above the annular electron beam generator, the bottom wall of said device having at least one opening out of which the bulk material particles fall and, from there, fall through the ring which is formed by the electron beam generator.