The coal is tested in different basis like ‘as received basis’, ‘dry basis’, ‘air dry basis’ etc. The testing can be done in one basis and the results can be represented in different basis by calculations.
Common recording standards (in alphabetical order):
Air-dried basis:
Results are calculated to the moisture condition of the coal after being allowed to air-dry (at room condition humidity). Usually written as “AD.”
As-determined (air-dried) basis:
Usually denoted as “adm” or “ADM.” Even after air-drying, coal typically contains some moisture, which is referred to as residual moisture.
As-received basis:
Results are calculated to the moisture condition of the coal sample when it arrived at the testing facility. Usually written as “AR.”
Dry basis:
Results are calculated to a theoretical base as if there were no moisture in the coal sample. This basis is commonly used in testing laboratories because of issues related to measuring moisture. Usually written as “DRY.”
Dry, ash-free basis:
Results are calculated to a theoretical base as if there were no moisture or ash in the coal sample. A calculation is made as if the coal was only composed of volatile matter and fixed carbon. Usually written as “DAF.”
Dry, mineral matter-free basis:
Data or results are calculated to a theoretical base as if there were no moisture or mineral matter in the coal sample. Calculation is needed to determine mineral-matter content rather than ash yield. In the United States, that equation uses the Parr formula:
Usually denoted as ‘DMMF’
Equilibrium-moisture basis:
Results are calculated to a moisture level of a coal sample established at equilibrium moisture conditions.
Moist, ash-free basis:
Results are calculated to a theoretical base as if there were no ash, but there is moisture, in the coal sample. Usually written as ‘MAF’
Moist, mineral-matter-free basis:
For some low-rank coals, this basis is used to calculate calorific value. It uses a theoretical base as if there were no mineral matter, but includes the moisture content of the coal sample. For this basis, a calculation is needed to determine mineral-matter content rather than ash yield. Usually written as ‘MMMF.’
Coal Analysis:
Coal is analysed in sponge plants for the followings
Ash fusion: Determines how coal ash will behave when heated in kiln or furnace.
Ash: Determines the amount of non-combustible material in a coal sample
Calorific value: Determines the heating potential of coal; usually expressed in Kcal /kg of coal
Fixed carbon: determines the amount of non-volatile carbon remaining in a coal sample after combustion
Hard-grove grindability: Determines how easily coal can be crushed
Moisture content: Explains tests and equations for different types of moisture content used in coal analysis
Proximate analysis: Determines moisture, volatile matter, ash and fixed carbon content.
Sulphur: Determines different types of sulphur in coal
Conversion of different results:
M = moisture,
A = Ash,
V = Volatile matter
FC = fixed carbon
As received basis (AR):
Analytic data calculated to the moisture condition of sample as it arrived at the laboratory and before any processing or conditioning. If sample has been maintained in a sealed state, so there has been no gain or loss, the as received basis is equivalent to the moisture basis as sampled.
Air dried basis (AD):
A means of expressing an analytical result based on the condition in which a solid mineral fuel is in equilibrium with atmospheric humidity.
Dry basis (D):
Ameans of expressing an analytical result based on the condition in which the solid mineral fuel is free from moisture
Dry ash free basis (DAF):
A means of expressing an analytical result based on a hypothetical condition in which the solid mineral fuel is considered to be free from both moisture and ash
Dry mineral matter-free basis (DMMF):
A means of expressing an analytical result based on a hypothetical condition which the solid mineral fuel is considered to free from both moisture and mineral matter
Moist ash-free basis (MAF):
A means of expressing an analytical result based on a hypothetical condition in which the solid mineral fuel is considered to be ash-free but with a moisture content equal to the moisture-holing capacity.
Moist mineral-free basis (MMF):
A means of expressing an analytical result based on a hypothetical condition in which the solid mineral fuel is considered to be mineral-matter-free but with a moisture content equal to the moisture-holding capacity
Moisture-holding capacity:
The moisture content of a solid mineral fuel in equilibrium with an atmosphere of 96% relative humidity at a temperature of 30℃ determined under specified condition.
Air drying:
A process of partial drying of coal to bring its moisture near to equilibrium with the atmosphere in the room in which further reduction and division of the sample will take place.
Conversion formula:
