In blast furnace, there is a steady increase in temperature from bottom to top.

Purpose of a blast furnace is to chemically reduce and physically convert iron oxides into liquid iron called "hot metal". At furnace temperature of about $1800^{o}C$, give or take $200^{o}C$, these liquid products are molten and trickle down to collect in the base of the furnace where they are extracted at regular intervals.