fixed carbon

Coal is a solid, carbon-rich fossil fuel, typically brown or black, found in stratified sedimentary deposits. It forms from the compaction and hardening of ancient plant matter, primarily peat, over geological time. The process of coalification, influenced by heat and pressure, transforms peat into lignite, then subbituminous, bituminous, and finally anthracite coal.

Coal's rank, or degree of coalification, is determined by tests like proximate analysis, which measures moisture, volatile matter, ash, and fixed-carbon content. Fixed carbon is the solid combustible residue remaining after volatile matter is expelled. Higher ranks generally have more fixed carbon and less moisture and volatile material, impacting their combustion properties and suitability for various uses like power generation and steel production.1234