Cokemaking

Cokemaking converts carefully selected coking coals into coke — the primary fuel, reductant, and structural support medium of the blast furnace. The process involves heating a blend of coking coals in the absence of air to temperatures of 1,000–1,100 °C over a coking time of 16–24 hours. The volatile matter driven off is captured and processed into valuable byproducts; the solid residue — a porous, high-carbon material — is pushed from the oven, quenched, and screened before dispatch to the blast furnace stockhouse.

A modern by-product coke oven battery consists of 40–100 individual ovens, each approximately 15–18 m long, 4–8 m tall, and 400–600 mm wide, arranged side-by-side and heated by combustion of coke oven gas in the flues between adjacent ovens. The battery operates continuously on a staggered pushing schedule — one oven is pushed approximately every 15–30 minutes — so that the blast furnace receives a steady supply of screened coke.

Steel plants with coke ovens are increasingly rare: many integrated producers have shifted to merchant coke purchasing as environmental regulations on oven emissions have tightened and battery replacement capital costs have escalated. Global coke production is approximately 640 million tonnes per year, dominated by China.