Coke

A coherent, cellular, carbonaceous residue remaining from the dry (destructive) distillation of a coking coal... used primarily as a fuel reductant in the blast furnace... Approximately 1300 lb of coke is consumed per ton of pig iron produced in the modern blast furnace, and about 200 lb of coke is required to melt a ton of pig iron in the cupola...

Coke is formed when coal is heated in the absence of air. During the heating in the range of 660-930F, the coal softens and then fuses into a solid mass. The coal is partially devolatilized in this temperature range, and further heating at temperatures up to 1830-2000F reduces the volatile matter to less than 1%...

(from "Coke" in McGraw-Hill Encyclopedia of Science and Technology vol 4 p 146 [1997])