ANS:A - counter current reactor

The Blast furnace is a counter current reactor. In a blast furnace, the movement of materials (the charge) and gases occurs in opposite directions. The charge, consisting of iron ore, coke, and limestone, descends from the top of the furnace, while hot air, known as the blast, is blown into the bottom of the furnace. This arrangement allows for efficient heat transfer and chemical reactions within the furnace. The counter current flow pattern in a blast furnace ensures that the hottest gases are in contact with the coolest charge at the top of the furnace, promoting the reduction of iron oxides and the formation of liquid iron at the bottom. As the charge descends through the furnace, it is gradually heated by the ascending hot gases, facilitating the melting and reduction processes. Therefore, the Blast furnace is classified as a counter current reactor.