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This standard is developed according to the rules specified in GB/T 1.1-2009.
This standard replaces GB/T 211-2007 Determination of Total Moisture in Coal. The following main technical changes have been made with respect to GB/T 211-2007 in addition to a number of editorial changes:
——Method C (drying in microwave) is deleted from determination methods (see 3.3 of Edition 2007);
——13mm sample is added in Method B1 (see 3.2.1; 3.2.1 of Edition 2007);
——Correction of air dried moisture loss in sample preparation is added (see 7.4);
——Informative annex titled "Determination of Total Moisture in Coal by Drying in Microwave" is added (see Annex A).
This standard has been redrafted and modified in relation to and is nonequivalent to ISO 589:2008 Hard Coal — Determination of Total Moisture.
This standard was proposed by the China National Coal Association.
This standard is under the jurisdiction of National Technical Committee on Coal Standardization Administration of China (SAC/TC 42).
The previous editions of this standard replaced by this standard include:
——GB 211-1963, GB 211-1984, GB/T 211-1996, GB/T 211-2007.
Determination of Total Moisture in Coal
1 Scope
This standard specifies determination of total moisture in coal in terms of method summary, reagents and materials, apparatus, sample, procedure, result calculation, method precision and test report.
In this standard, drying under nitrogen (Method A1 and Method B1) is suitable for all coals while drying in air (Method A2 and Method B2) is suitable for soft coal (excluding coals susceptible to oxidation) and blind coal.
In this standard, Method A1 serves as an arbitration method.
Note: this standard also provides drying in microwave for quick determination of full moisture and this method is suitable for soft coal and lignite, as shown in Annex A.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 212 Proximate Analysis of Coal
GB/T 474 Method for Preparation of Coal Sample
GB/T 19494.2 Mechanical Sampling of Coal Part 2: Method for Sample Preparation
3 Method Summary
3.1 Method A (two-stage method)
3.1.1 Method A1: drying in nitrogen
Some amount of 13mm sample is weighed and dried at temperature not exceeding 40℃ until mass is constant, crush the air-dried sample to 3mm nominal top size and then dry it in a nitrogen flow at 105℃~110℃ until mass is constant. Full moisture is calculated by the mass loss of sample after two-stage drying.
3.1.2 Method A2: drying in air
Some amount of 13mm sample is weighed and dried at temperature not exceeding 40℃ until mass is constant, crush the air-dried sample to 3mm nominal top size and then dry it in an airflow at 105℃~110℃ until mass is constant. Full moisture is calculated by the mass loss of sample after two-stage drying.
3.2 Method B (single-stage methods)
3.2.1 Method B1: drying in nitrogen
Some amount of 6mm (or 13mm) sample is weighed and dried in a nitrogen flow until mass is constant at 105℃~110℃. The full moisture is calculated from the loss in mass of the sample.
3.2.2 Method B2: drying in air
Some amount of 13mm (or 6mm) sample is weighed and dried in an airflow until mass is constant at 105℃~110℃. The full moisture is calculated from the loss in mass of the sample.
4 Reagents and Materials
4.1 Anhydrous calcium chloride: chemically pure, granular.
4.2 Allochroic silicagel: industrial product.
4.3 Nitrogen: having purity of not exceeding 99.9% and oxygen content of less than 0.01%.
4.4 Weighing tray: made of heat- and corrosion-resistant materials such as enamel, stainless steel, galvanized steel sheet or aluminum plate, capable of holding 500g of sample and with unit area loading not exceeding 1g/cm2.
4.5 Glass weighing bottle: with a diameter of 70mm, a height of 35mm~40mm and a tight ground cover.
4.6 Sampler: suitable for 13mm or 6mm sample and with an opening at least three times as large as the particle size.
5 Apparatus
5.1 Air-dried oven: with automatic temperature control and blowing device, capable of being controlled at a temperature of 30℃~40℃ and 105℃~110℃, with air inlet and outlet and sufficiently rapid rate of atmosphere change, over 5 times per hour.
5.2 Nitrogen-flushed oven: with automatic temperature regulating device, capable of be controlled at a temperature of 105℃~110℃ and holding an amount of weighing bottle and with smaller free space and nitrogen inlet and outlet and rate of atmosphere change over 15 times per hour.
5.3 Analytical balance: capable of weighing to 0.001g.
5.4 Industrial balance: capable of weighing to 0.1g.
5.5 Dryer: filled with allochroic silicagel or granular anhydrous calcium chloride.
5.6 Flowmeter: with a measuring range of 100mL/min ~1000 mL/min.
5.7 Drying tower: with a capacity of 250mL and filled with allochroic silicagel or granular anhydrous calcium chloride.
Foreword i
1 Scope
2 Normative References
3 Method Summary
4 Reagents and Materials
5 Apparatus
6 Sample
7 Procedure
8 Precision of Method
9 Test Report
Annex A (Informative) Determination of Total Moisture in Coal by Drying in Microwave
