Q.Name different zones in the Blast furnace. Write the reactions taking place in them.

Step 1. Zone of combustion (5-10 m from the furnace bottom, around 2000 K, the hottest zone). Hot air blown in through the tuyeres reacts with coke from the charge: C + 1/2 O2 -> CO, DeltaH = -220 kJ (strongly exothermic, which is why this zone reaches the highest temperature). Some of the CO formed dissociates back to fine carbon: 2CO -> 2C + O2. The resulting hot, CO-rich gas rises through the furnace and acts as both fuel and reducing agent for the zones above.

Step 2. Zone of reduction (22-25 m, near the top, around 900 K). Iron(III) oxide is reduced to spongy metallic iron, mainly by the rising carbon monoxide: Fe2O3 + 3CO -> 2Fe + 3CO2; a smaller amount is reduced directly by carbon: Fe2O3 + 3C -> 2Fe + 3CO.

Step 3. Zone of slag formation (around the 20 m level, around 1200 K). The gangue in the ore (silica, alumina, phosphates) is converted into slag. Limestone in the charge first decomposes: CaCO3 -(heat)-> CaO + CO2, and the resulting quicklime reacts directly with the gangue: CaO + SiO2 -> CaSiO3, and 12CaO + 2Al2O3 -> 4Ca3AlO3 + 3O2, forming a molten calcium-silicate/aluminate slag (usable afterward for road foundations).

Step 4. Zone of fusion (around the 15 m height). Manganese dioxide and calcium phosphate present in the ore are reduced to manganese and phosphorus respectively, and some silica is reduced to silicon. The spongy iron descending through this zone melts and absorbs these impurities (C, Si, Mn, P, S). The denser molten iron collects at the furnace bottom, while the lighter molten slag floats on top, and the two are tapped off through separate outlets.

Note on the source's own internal inconsistency: the chapter's own summary Table 8.10 assigns a slightly DIFFERENT temperature-to-change mapping (900K=reduction by CO, 1200K=lime decomposition, 1500K=reduction by C, 2000K=slag formation) than the running-text zone account given above (which separately places slag formation at ~1200K and fusion/reduction-by-C at ~1500K, with combustion at the ~2000K bottom). Both versions are given here rather than silently picking one, since this is a genuine discrepancy within the source rather than a transcription choice.

Working through the four named zones and their reactions from Section 8.9.2's running-text account, cross-checked against (and honestly flagging a discrepancy with) the chapter's own Table 8.10 summary

• Naming only the reactions without the zone NAMES (combustion/reduction/slag formation/fusion) the question specifically asks for.
• Mixing up which reactions belong in which zone by conflating the running-text account with Table 8.10's differently-ordered temperature summary, without noticing the two disagree.