Total moisture contain on material like coal usually analyze as received, either directly or step by step, but for other material is analyze on the dry bases on sample that treat by heating first and grinding to smooth.
Annalist here difficult to measure on create a method on examine of sample for applying for coal as overall on the real condition that have big form and wet. Generally total moisture contain examine on two-step so the analyze method named by two stage determination.
After the first step has done on sample preparation by weighing sample then dry on room temperature until get constant weight (the difference between last weighing and before last must less than 0.1%). Weight loss is counted on percentage and name as air dry loss (ASTM) or free moisture (ISO/BS/AS).
The goal of constant weight in order the sample don’t change the weight anymore (absorb or vaporize) on the next preparation step like milling and dividing, so the result of examination the total moisture become bigger.
After reach of constant weight, sample is milled to certain particle size, take a part and sent to the laboratory to analyse the residual moisture by heating the sample in oven on temperature 105 to 110oC for 3 hours while flowing of nitrogen gas.
Total Moisture is counted by formula:
TM = ADL + RM * (1 – ADL/100)
Where:
TM = total moisture on % (as received basis – ar)
ADL = air-dry loss on % (as received bases – ar)
RM = residual moisture on % (air dried bases – ad)
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