Patent ID: 8173064

Claim:
Method for operating a shaft furnace, whereby an upper section of the shaft furnace is charged with raw materials which due to gravity descend inside the shaft furnace while an atmosphere prevailing within the shaft furnace causes part of the raw materials to melt and/or to be reduced, and in a lower section of the shaft furnace a process gas is injected so as to at least partly modify the atmosphere prevailing in the shaft furnace, whereby the injection of the process gas is dynamically modulated in a manner whereby in the modulation, the process pressure p and/or volume flow {dot over (V)}, are varied at least intermittently within a time span of ≦40 s and whereby the process gas is injected into the blast furnace through at least two different channels, a first process variable serving to control the process-gas component being injected along the first channel is dynamically modulated and a second process variable serving to control the process-gas component being injected along the second channel is dynamically modulated, the first and the second process variables are identical process variables modulated differently or the first and the second process variables are mutually different but subjected to identical modulation, and whereby the first and the second process variables are periodically modulated with an identical cycle time T while their relative phase is shifted by a specific value.