Q12Engineering Chemistry

Proximate analysis is the absolutely fundamental, universally standardized laboratory procedure utilized to rapidly and highly practically evaluate the overall commercial quality, absolute heating potential, and industrial suitability of solid coal. Unlike ultimate analysis (which determines the exact elemental chemical makeup like C, H, O, N, S), proximate analysis strictly determines the physical, macroscopic composition of the coal via sequential thermal heating stages.

1. Determination of Moisture

Exactly $1\text{ gram}$ of finely powdered, air-dried coal is rigorously weighed explicitly in a silica crucible and systematically heated completely in an electric hot-air oven precisely maintained between $105^{\circ }\text{C}$ and $110^{\circ }\text{C}$ for exactly one hour. The crucible is subsequently cooled rigidly in a dry desiccator and re-weighed. The absolute loss in physical weight strictly corresponds precisely to the superficial moisture entirely evaporated.

2. Determination of Volatile Matter (VM)

The completely moisture-free coal sample from the previous step is heavily covered tightly with a strict, tight-fitting lid to absolutely prevent oxidation. It is then violently heated exactly inside an extremely hot electric muffle furnace rigidly maintained precisely at $925^{\circ }\text{C}\pm 20^{\circ }\text{C}$ for exactly 7 minutes. It is cooled and weighed. The massive further loss in weight strictly corresponds entirely to the complex combustible hydrocarbon gases (methane, hydrogen, etc.) that violently escaped.

3. Determination of Ash

The residual coal sample is now completely uncovered (the lid is strictly removed) and violently heated exactly in the highly oxygen-rich muffle furnace at $700^{\circ }\text{C}-750^{\circ }\text{C}$ for approximately 30 minutes, or until the physical weight becomes completely constant. This aggressive aerobic heating entirely burns away all combustible carbon. The remaining heavy, incombustible mineral residue left in the crucible is strictly defined as Ash (silicates, iron oxides, etc.).

4. Calculation of Fixed Carbon

Fixed carbon represents the absolute pure combustible solid carbon intimately bonded in the coal matrix. It is strictly never determined directly by physical experiment; it is absolutely always calculated rigorously by mathematical difference.