SANS 5924-2009 Moisture content of coal samples intended for general analysis (vacuum-oven method)《一般分析用煤样的水含量(真空烘箱法)》.pdf

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3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-21948-2 SANS 5924:2009 Edition 2SOUTH AFRICAN NATIONAL STANDARD Moisture content of coal samples intended for general analysis (vacuum-ove

4、n method) Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001 Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 5924:2009 Edition 2 Ta

5、ble of changes Change No. Date Scope Foreword This South African standard was approved by National Committee SABS SC 27B, Solid mineral fuels Test methods, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This document was published i

6、n April 2009. This document supersedes SABS SM 924:1978 (edition 1). This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 5924:2009 Edition 2 1 Moisture content of coal samples intended for general analysis (vacuum-oven method) 1 Scope This sta

7、ndard specifies the vacuum-oven method for the determination of the moisture content of coal samples intended for general analysis. NOTE The determination of the moisture content of the laboratory-conditioned sample provides for the calculation of the results of general analyses (also determined on

8、the laboratory-conditioned sample) to other bases, e.g. dry, ash-free. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced

9、document (including any amendments) applies. Information on currently valid national and international standards can be obtained from the SABS Standards Division. SANS 18283, Hard coal and coke - Manual sampling. 3 Principle Coal passing a 212 m test sieve is heated to constant mass in a vacuum-oven

10、 at a temperature of 105 C to 110 C and the moisture content of the coal is calculated from the loss in mass. 4 Apparatus 4.1 Oven A vacuum-oven fitted with a pressure gauge, and in which a temperature of 105 C to 110 C and an absolute pressure of less than 6,7 kPa is maintained. The air inlet shall

11、 include a constriction that permits the slow re-admission of the air. 4.2 Weighing vessel A shallow cylindrical vessel of diameter at least 30 mm and that has a well-fitting cover. The vessel and cover shall be of glass with mating surfaces that are ground, or of a non-corrodible and heat resistant

12、 material. The vessel and its cover shall be clean, dry, and accurately tared. NOTE A silica dish, of the specified diameter and of depth 10 mm to 15 mm, may be used if suitable precautions are taken to avoid absorption of moisture by the dish. This standard may only be used and printed by approved

13、subscription and freemailing clients of the SABS.SANS 5924:2008 Edition 2 2 4.3 Balance, that has a sensitivity of 0,1 m. 4.4 Desiccant, that has fresh (or freshly regenerated) self-indicating silica gel. 4.5 Desiccator, that contains the desiccant. 5 Procedure 5.1 Condition the sample prepared in a

14、ccordance with SANS 18283, i.e. expose the sample in a thin layer for at least 30 min to allow the moisture content to attain equilibrium with the laboratory atmosphere. 5.2 Thoroughly mix (preferably by mechanical means) the conditioned sample for at least 1 min. 5.3 Uniformly spread about 1 g of t

15、he conditioned sample in the weighing vessel, replace the cover, and determine the initial mass m 2 , of the vessel and contents. 5.4 Place the cover in the desiccator, and heat the uncovered vessel and the test sample in the oven until their mass remains constant (1 h is normally sufficient), re-ad

16、mitting air to the oven through a drying tower packed with the desiccant. Close the vessel with its cover, allow it to cool on a metal plate for 10 min, transfer it to the desiccator and, after a further period of 10 min, determine its mass, m 3 . 6 Calculations Calculate, to the nearest 0,1 %, the

17、moisture content of the test sample as follows: Moisture content, % (m/m) = 100 1 2 3 2 m m m mwhere m 1 is themass of the empty vessel plus cover, in grams; m 2 is the initial mass of the vessel plus cover plus test sample, in grams; m 3 is themass of the vessel plus cover plus test sample after he

18、ating, in grams. Report the result (preferably the mean of duplicate determinations) to the nearest mass fraction of 0,1 %. This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 5924:2009 Edition 2 3 7 Precision The results of duplicate determin

19、ations shall not differ by more than the appropriate of the values given in table 1. Table 1 Precision of results 1 2 Moisture content % (m/m) Repeatability (same operator and same apparatus) % absolute Less than 5 0,10 5 and over 0,15 NOTE Limits for reproducibility (different operators and apparat

20、uses) have not yet been established because results obtained in different laboratories depend on the humidity conditions, which may vary from laboratory to laboratory. SABS This standard may only be used and printed by approved subscription and freemailing clients of the SABS. This page has been lef

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