Published: Jan 2007
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THE RESULTS OF A COAL ANALYSIS MAY BE REPORTED ON ANY OF A number of bases, differing from each other in the manner by which moisture and ash is treated. Except for data reported on a dry basis, it is essential that an appropriate moisture content be given in the data report. This would avoid ambiguity and provide a means for conversion of data to other bases. These bases are defined in ASTM D121 and include the following:
As-determined Basis (ad)The basis for analytical data obtained from an analysis sample of coal or coke after conditioning and preparation to Number 60 (250 m) sieve, in accordance with ASTM D 2013. As-determined data represent the numerical values obtained at the particular moisture level in the analysis sample at the time of the analysis.
As-received Basis (ar)The basis for analytical data calculated to the moisture condition of the sample as it arrived at the laboratory and before any processing or conditioning. If the 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.
Dry Basis (d)The basis for analytical data calculated to a theoretical basis of no moisture associated with the sample. The numerical value as established in ASTM D 3173 or D 5142 is used for converting the as-determined data to a dry basis.
Dry, Ash-free Basis (daf)The basis for data calculated to a theoretical basis of no moisture or ash associated with the sample. Numerical values as established by ASTM D 3173 and D 3174, or D 5142, are used for converting the asdetermined data to a moisture- and ash-free basis.
Equilibrium Moisture BasisThe basis for data calculated to the moisture level established as the equilibrium moisture. Numerical values as established by ASTM D1412 are used for the calculation to an equilibrium moisture basis.
Paper ID: MNL11273M