The nonvolatile matter in coal minus the ash. Fixed carbon is the solid residue other than ash obtained by prescribed methods of destructive distillation of a coal. Fixed carbon is the part of the total carbon that remains when coal is heated in a closed vessel until all matter is driven off. Actually fixed carbon is combustible residue remaining after removal of moisture, ash, and volatile materials from coal, coke, and bituminous materials.
This test covers the determination of moisture, volatile matter, and ash and the calculation of fixed carbon on natural bitumen sampled and prepared by prescribed methods and analyzed according to ASTM D3172 established procedures.
The fixed carbon is a calculated value. It is the resultant of the summation of percentage moisture, ash, and volatile matter subtracted from 100. All percentages shall
be on the same moisture reference base.
Fixed carbon % = 100 – (moisture % + ash % + volatile matter %)