Measurement of GCV in different basis
The variables are measured in weight percent (wt. %) and are calculated in several basis, they are
AR (as-received) basis is the most widely used basis in industrial applications. AR basis puts all variables into consideration and uses the total weight as the basis of measurement.
AS RECEIVED BASIS (AR) = TM+IM+ASH+VM+FC+S (Includes all moistures)
AD (air-dried) basis is to neglect the presence of moistures other than inherent moisture while DB (dry-basis) leaves out all moistures, including surface moisture, inherent moisture, and other moistures.
AS DRIED BASIS (AD) = 0+IM+ASH+VM+FC+S (Includes Inherent moisture)
DAF (dry, ash free) basis is to neglect all moisture and ash constituent in coal
AS DRY ASH FREE (DAF) = 0+0+0+VM+FC+0 (Excludes all moisture & Ash)
DMMF (dry, mineral-matter-free) basis leaves out the presence of moisture and mineral matters in coal, for example: quartz, pyrite, calcite, etc. Mineral matter is not directly measured but may be obtained by one of a number of empirical formula based on the ultimate and proximate analysis.
AS DRY BASIS (DB) = 0+0+ASH+VM+FC+S (Excludes all moisture)
(TM=Total Moisture, IM=Inherent Moisture, VM=Volatile Matter, FM=Fixed Carbon, S=Sulphur