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 be temporarily connected via a valve connecting the reservoir can generate for instance a short pulse increasing the pressure by 1 5 to 2 5 bar meaning that for the duration of that pulse the process gas pressure is about 12 bar within the blast furnace this pulse generates an energy spike that melts caking and slag in the peripheral area of the reaction zone and or punches holes through the layer of caking and slag since that energy spike pumps oxygen into the slag layer in the reaction zone it causes oxidizing reactions with the slag layer the loosening of the slag permits better through gassing throughout the blast furnace at a minimum slag formation can be reduced by adding to.