Coal Terms

RAW COAL:
Raw coal is unprocessed coal extracted naturally from a coal mine.

SCREENED COAL:
Screened coal is raw coal that has undergone sorting and screening processes.

SCREENED COAL:
Screened coal is coal that has been passed through screens with specific mesh sizes and classified within specific size limits.

CLEANED COAL:
Cleaned coal is coal that has undergone a cleaning process using either a wet or dry system.

WASHED COAL:
Washed coal is coal that has undergone a wet cleaning process.

TOTAL MOISTURE (MOISTURE CONTENT):
The amount of moisture that can be removed from a coal sample under standard conditions.

INTRINSIC MOISTURE (Intrinsic Moisture - Hygroscopic Moisture):
The moisture lost by an air-dry coal sample until it reaches a constant weight when heated to 105°C in an oxygen-free environment.

FREE MOISTURE (Surface Moisture - Crude Moisture):
The moisture lost by raw coal until it becomes air-dried coal; this is also referred to as crude moisture.

MOISTURE IN AIR-DRY COAL:
The moisture content of a coal sample that has reached approximately equilibrium with the surrounding air.

TOTAL ASH:
The percentage of the total weight of mineral matter remaining after the complete combustion of a coal sample.

FIXED ASH:
These are the mineral substances that cannot be removed from coal by physical means.

GAS:
This is the mass lost during the heating and distillation of coal in an oxygen-free (anaerobic) environment. It consists of the sum of volatile matter and moisture.

VOLATILE MATTER:
This is the value obtained by subtracting the moisture content from the total gas content in the coal.

FIXED CARBON:
The value obtained by subtracting the total of moisture, ash, and volatile matter from 100.

ELEMENTAL CARBON:
The value consisting of the total of free and bound carbon present in the coal’s composition.

PURIFIED COAL:
The usable portion of coal, consisting of the total of Volatile Matter and Fixed Carbon.

COKE:
The sum of the Fixed Carbon and Ash content in coal.

COKE QUALITY:
A description of the shape and color of the coal remaining after gas analysis.

TOTAL SULFUR:
The percentage of sulfur contained in all sulfur compounds (sulfate, organic, free, pyrite, chalcopyrite, etc.) within a coal sample.

SULFUR IN ASH (Non-combustible Sulfur):
The percentage of sulfur remaining in the ash obtained by completely burning the coal sample at a maximum temperature of 850°C, present in the form of sulfate compounds.

BURNING SULFUR:
The percentage of sulfur present in the combustion gases as sulfur compounds following the complete combustion of a coal sample at a maximum temperature of 850°C.

UPPER (HIGH) HEAT VALUE (Calorific Value):
The heat released as a result of the complete combustion of a coal sample in a calorimeter bomb, expressed in kcal/kg.

LOWER HEAT VALUE (Calorific Value):
The heat released when a coal sample is completely burned in a calorimeter bomb, expressed in kcal/kg, calculated by subtracting the sum of the heat of condensation of water formed from the combustion of hydrogen in the coal and the moisture content of the coal from the Upper Heat Value.