Start-up of a cupola furnace.
After leaving the bed coke to burn through and filling it up to the required height, short blasting of the furnace before feeding the charge make-up has proved to be beneficial. The blowers are operated at approx. 30 % of their normal output for 3 to 5 minutes in order to blow out the sulfur that is contained in the not yet calcined coke, as well as the loose unsintered coke cinder. This reduces the sulfur content in the first batch of iron.
After inspection of the bed coke height and after burning it through completely, i.e. after the uppermost coke layer has become a cherry-red color, the complete charges of coke, iron, and fluxes can be fed into the furnace with the blowers not operating. Upon complete charging of the furnace, the actual blow-in phase is started. In this way it is ensured that even the iron first tapped has the required chemical composition and temperature.