of the phase shift thus selected the incremental amount of the supplemental reducing agent injected in the vortex zone has a head start on the next following oxygen pulse and is to a degree available for the conversion while the trailing oxygen pulse can bring about the conversion of the supplemental reducing agent before the latter leaves the vortex zone as a consequence a reliably high conversion rate is achievable for the supplemental reducing agent concurrently with an increased injection rate leading to improved through gassing in the shaft furnace the example explained with the aid of fig1 to 5 of a dynamic modulation of the injection of the process gas and other components merely represents a fraction of the possibilities to implement the dynamic modulation according to the invention as will be evident from the various design examples the characterizing features of the invention disclosed in the above description and in the patent claims can serve as key elements individually and in any combination in the implementation of the invention in its various configurations assuming for example that the shaft furnace is a blast furnace with an internal pressure of about 2 to 4 bar the process gas may be injected at a continuous pressure of about 10 bar for a pulsed modulation a reservoir with a pressure for instance of 20 bar may.