Coke is a low-impurity, high-carbon fuel, usually made from coal. It is the solid carbonaceous material derived from the destructive distillation of low-ash, low-sulfur bituminous coal.
Boxes made of charcoal are gray, hard, and porous. While coke can form naturally, the commonly used form is man-made. The form known as petroleum coke, or pet coke, is derived from petroleum refinery coke units or other cracking processes.
Among its uses are:
- Coke is used in the preparation of the producer gas which is a mixture of carbon monoxide (CO) and nitrogen (N2). Gas production occurs by passing air over hot coke. Coke is also used to make water gas.
- Coke is used as a fuel and as a reducing agent in the smelting of iron ore in a blast furnace. The carbon monoxide produced by its combustion reduces the iron oxide (hematite) in the production of the iron product.
- Coke is commonly used as a fuel for blacksmithing.
Coke was used in Australia in the 1960s and early 1970s for home heating.
Since the smoke-producing components are expelled during coking of the coal, the coke forms a desirable fuel for stoves and furnaces where conditions are not suitable for the complete combustion of the bituminous coal itself. Coke can burn producing little or no smoke, whereas bituminous coal would produce a lot of smoke. Coke is widely used as a substitute for coal in domestic heating after the creation of smoke-free zones in the UK.
Discovered by accident to have superior heat shielding properties when combined with other materials, coke was one of the materials used in heat shielding in NASA's Apollo Command Module. In its final form, this material was called AVCOAT 5026-39. This material has most recently been used as a heat shield on the Mars Pathfinder vehicle. Although it was not used for the space shuttle, NASA had been planning to use coke and other materials for the heat shield for its next-generation spacecraft, Orion.
