Q.Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.

The furnace runs hottest (~2170 K) near the bottom where coke burns in the hot air blast, and progressively cooler toward the top, so different reactions dominate at different heights: reduction of iron oxides by CO in the cooler upper/middle zones, decomposition of limestone and slag formation in the middle, and final reduction of FeO to molten iron plus slag formation lower down. …

Step 1 – Overall setup

The blast furnace is charged from the top with a mixture of roasted iron ore (mainly haematite, $Fe_2O_3$), coke, and limestone ($CaCO_3$). A blast of hot air is blown in near the bottom, through nozzles called tuyeres. As the charge descends, it passes through zones of progressively increasing temperature (roughly 500 K near the top to over 2000 K near the bottom), and different reactions occur in each zone.

Step 2 – Combustion zone (near the tuyeres, hottest, ~2170 K)

Coke burns in the blast of hot air:

The $CO_2$ formed then reacts with excess hot coke just above:

This carbon monoxide is the main reducing agent that rises up through the furnace.

Step 3 – Reduction zone (upper/cooler region, ~500–800 K) — indirect reduction by CO

As CO rises into the cooler upper zones, it progressively reduces haematite:

(and partially, $Fe_2O_3 + CO \rightarrow 2FeO + CO_2$)

Step 4 – Middle zone (~900–1500 K) — limestone decomposition

Limestone charged along with the ore decomposes:

Step 5 – Lower zone (~1500–1600 K) — direct reduction and slag formation

Any remaining FeO is reduced directly by carbon at this higher temperature:

The lime (CaO) formed combines with silica gangue to form slag:

Step 6 – Collection …

Walk down the furnace from the hot combustion zone at the bottom (coke burns, generates CO) to the cooler zones above (iron oxides reduced stepwise by CO, then limestone decomposes an …

• Writing only the final reduction $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$ and omitting the actual STEPWISE reduction sequence ($Fe_2O_3\rightarrow Fe_3O_4\rightarrow FeO\rightarrow Fe$) and the slag-forming/limestone reactions the question specifically asks for. …