Bessemer Converter
The blast furnace was responsible for transforming iron ores into merchant iron, i.e- iron with 4% - 4.5% carbon, which was also called pig iron because the originally, the cooled large, central, and adjoining smaller ingots resembled a sow and suckling piglets
This pig iron had too much carbon content to be made into anything useful and so had to have its carbon content and other impurities reduced.
In the current timeline, this was done by repeatedly hammering the iron and thus literally beating the impurities out of it in the form of slag.
While in Alexander's previous time, the first industrial process of carbon removal was done by the puddling process, where workers called puddlers would use long oar-shaped tools to stir the molten iron like one would stir a pot of curry.