Coke
Definition and meaning of Coke in chemistry.
Coke is a hard, porous, carbon-rich solid fuel made by heating bituminous coal (or heavy petroleum residues) to about 1000-1100°C in the near-total absence of air, driving off volatile matter and leaving behind a nearly pure carbon residue.
In more detail
This heating process, called destructive distillation or coking, removes water, tars, and volatile hydrocarbons (which are collected as valuable byproducts such as coal tar and coke-oven gas), leaving a strong, porous mass that is 85-98% carbon plus mineral ash. Because it lacks the volatile matter and much of the sulfur present in raw coal, coke burns hotter and more cleanly, and its rigid, porous structure lets it support heavy loads without crushing at furnace temperatures. These properties make coke indispensable in metallurgy, where it serves simultaneously as fuel, structural support, and chemical reducing agent.
Key facts
| Formula | C (predominantly carbon, ~85-98%, with mineral ash) |
|---|---|
| Field | Inorganic Chemistry |
| Production temperature | ~1000-1100 °C, absence of air (coking) |
| Primary use | Blast furnace fuel and reducing agent in ironmaking |
In a blast furnace, coke is burned with a blast of hot air to form carbon monoxide, which then reduces iron(III) oxide to molten iron: Fe2O3(s) + 3CO(g) -> 2Fe(l) + 3CO2(g).
Frequently asked questions
How does coke differ from coal?
Coal is the raw sedimentary rock containing moisture, volatile hydrocarbons, and carbon; coke is what remains after coal is heated without air to drive off those volatiles, leaving a harder, nearly pure carbon material.
Why is coke preferred over raw coal in blast furnaces?
Coke burns hotter and cleaner, contains less sulfur, and stays strong and porous at high temperature, so it can support the ore and limestone burden while also fueling and chemically reducing the iron ore.