Below is a list of Blast Furnaces manufacturers from St. Marys, Pennsylvania. Blast furnaces are large towers or cylinders that have a heat-resistant lining. These furnaces force gusts of hot air and gases up through the furnace load. As air is pushed into the furnace from the bottom, ore, fuel and limestone are pushed in through the top. This allows the chemical reaction to occur as the ore, fuel and limestone move down the cylinder. The result is molten metal and slag at the bottom of the furnace, while flue gases move upward and exit through the top of the blast furnace.