1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58moisture content Part 2: Indirect gravimetric method for moisture in the analysis sampleICS 73.040B
2、rown coals and lignites Determination of BRITISH STANDARDBS ISO 5068-2:2007BS ISO 5068-2:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2007 BSI 2007ISBN 978 0 580 50195 1Amendments issued since publicationAmd. No. Date Comme
3、ntscontract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 5068-2:2007.The UK participation in its preparation was entr
4、usted to Technical Committee PTI/16, Solid mineral fuels.A list of organizations represented on PTI/16 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a Reference numberISO 5068-2:2007(E)INTERNATIONAL STANDARD ISO5068-2First ed
5、ition2007-02-01Brown coals and lignites Determination of moisture content Part 2: Indirect gravimetric method for moisture in the analysis sample Charbons bruns et lignites Dtermination de lhumidit Partie 2: Mthode gravimtrique indirecte pour lhumidit de lchantillon danalyse BS ISO 5068-2:2007ii iii
6、Contents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Definitions . 1 4 Principle. 1 5 Reagent 1 6 Apparatus 2 7 Sample . 4 8 Procedure 4 9 Expression of results . 4 10 Precision of method . 5 11 Test report . 5 Annex A (informative) Nitrogen-purification train. 6 BS ISO 5068-2:2007iv F
7、oreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a te
8、chnical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters
9、of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated
10、 to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible f
11、or identifying any or all such patent rights. ISO 5068-2 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5, Methods of analysis. This first edition of ISO 5068-2, together with ISO 5068-1, cancels and replaces ISO 5068:1983, which has been technically revised. ISO
12、 5068 consists of the following parts, under the general title Brown coals and lignites Determination of moisture content: Part 1: Indirect gravimetric method for total moisture Part 2: Indirect gravimetric method for moisture in the analysis sample BS ISO 5068-2:20071Brown coals and lignites Determ
13、ination of moisture content Part 2: Indirect gravimetric method for moisture in the analysis sample 1 Scope This International Standard specifies a method for the determination of the moisture content in the analysis sample of brown coals and lignites using an indirect gravimetric method. 2 Normativ
14、e 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 document (including any amendments) applies. ISO 1213-2, Solid mineral fuels Voca
15、bulary Part 2: Terms relating to sampling, testing and analysis ISO 5069-2, Brown coals and lignites Principles of sampling Part 2: Sample preparation for determination of moisture content and for general analysis 3 Definitions For the purpose of this document, the definitions given in ISO 1213-2 ap
16、ply. 4 Principle A test portion of the general analysis test sample is dried to constant mass at a temperature of 105 C to 110 C in an atmosphere of nitrogen. The moisture content of the analysis sample is calculated from the loss in mass of the test portion. NOTE Brown coals and lignites are hygros
17、copic and therefore their moisture content varies with change of humidity of the atmosphere. Hence, the moisture content of the analysis sample is determined whenever test portions are weighed out for other analyses sample, for example volatile matter, calorific value, carbon and hydrogen, etc. 5 Re
18、agent 5.1 Desiccant, fresh or freshly regenerated and preferably self-indicating. Suitable desiccants are magnesium perchlorate and silica gel. WARNING Magnesium perchlorate is a strong oxidizing agent. Do not attempt to regenerate the absorbent. Do not permit contact with organic materials or a red
19、ucing agent. BS ISO 5068-2:20072 5.2 Nitrogen, high-purity, dry, with a maximum oxygen content of 30 l/l. NOTE Commercial nitrogen of this purity is available. See Annex A for details. 6 Apparatus 6.1 Oven, capable of being controlled at a temperature of 105 C to 110C and with the provision for the
20、nitrogen to pass through it at a flow rate of approximately 15 times the oven volume per hour and of lowest practical volume, i.e. minimum free space. Before using a new oven, carry out a temperature profile through the interior and take care to insert samples only where the temperature is known to
21、be 105 to 110C. A suitable oven is illustrated in Figure 1. BS ISO 5068-2:20073Dimensions in millimetres Key 1 nitrogen outlet 3 thermometer tube 2 space for heating element 4 copper gauze, having apertures of nominal size 0,25 Figure 1 Typical nitrogen oven BS ISO 5068-2:20074 6.2 Weighing dish, a
22、shallow dish, of silica or glass, with ground edges and fitted with a ground-glass cover, or a non-corrodible, heat-resistant material with a well-fitting lid. The diameter of the dish shall be such that the mass of coal layer does not exceed 0,15 g/cm2for 1 g to 2 g of the analysis sample. 6.3 Bala
23、nce, sensitive to 0,001 g. 6.4 Flow meter, capable of measuring the rate of flow nitrogen through the oven. 6.5 Drying tower, 250 ml capacity, packed with magnesium perchlorate or silica gel for drying the nitrogen. 6.6 Cooling vessel, for example a desiccator without desiccant, containing a metal p
24、late, preferably of aluminium or copper. The vessel may be provided with a means to pass dry nitrogen through it during the cooling period. 7 Sample The analysis sample is prepared in accordance with ISO 5069-2 and generally ground to pass a 0,212 mm sieve. 8 Procedure Raise the temperature of the o
25、ven to between 105 C and 110 C while passing nitrogen through it at a rate to provide 15 oven-volume changes per hour. Weigh a clean, dry, empty weighing dish with its lid to the nearest 0,001 g. Spread into it an even layer of 1 g to 2 g of the analysis sample (Clause 7). Cover and reweigh to the n
26、earest 0,001 g. Place the uncovered vessel and its lid in the oven for 3 h or until constant mass is obtained. NOTE The time required to achieve constant mass can be assessed by individual laboratories for each coal rank. Remove the dish with the dried sample from the oven and replace the cover imme
27、diately. If the size of the oven allows this, replace the cover while the dish is still in the oven. Allow the covered dish to cool on a thick metal plate for no longer than 5 min. Transfer the dish to a cooling vessel and allow it to cool to room temperature (approximately 20 min). As soon as the s
28、ample reaches room temperature, reweigh to the nearest 0,001 g. 9 Expression of results 9.1 The moisture content, Mad, of the analysis sample, expressed as a mass, is calculated using Equation (1): 23ad21100mmMmm=(1) where m1is the mass of weighing dish and its lid, expressed in grams; m2is the mass
29、 of weighing dish, lid and sample before heating, expressed in grams; m3is the mass of weighing dish, lid and sample after heating, expressed in grams. 9.2 Take as the final result of the test the arithmetic mean of the results of duplicate determinations. Report the result to the nearest 0,1 %. BS
30、ISO 5068-2:2007510 Precision of method 10.1 Repeatability limit The results of duplicate determinations, carried out in the same laboratory by the same operator using the same apparatus on the same sample within short intervals of time, shall not differ by more than 0,3 %. 11 Test report The test re
31、port shall contain the following information: a) identification of the sample tested; b) reference of the standard used; c) result and the method of expression used; d) date of the test. BS ISO 5068-2:20076 Annex A (informative) Nitrogen-purification train It is essential that the nitrogen used for
32、ventilating the minimum-free-space oven should be comparatively pure, since even the small residual amount of oxygen that is found in commercial nitrogen can cause oxidation and hence produce a low result in the moisture figure determined by the loss in mass on drying. A good purification train for
33、nitrogen is, therefore, required. A suitable one is described here, which is capable of dealing with at least 600 ml per minute at a pressure of a few millimetres mercury gauge. A convenient source of the gas is a cylinder of compressed nitrogen. The purification train consists of a quartz tube 500
34、mm long and with an internal diameter of 37 mm, containing 1,2 kg of reduced copper in wire form. The purification tube is heated by a suitable furnace, which encloses the tube to a length of 380 mm and allows the part of the tube containing the copper wire filing to protrude approximately 80 mm at
35、exit end in order to produce a temperature drop in the gas stream. The reduced copper is heated to approximately 500 C. The last traces of oxygen are removed by the very large surface area of copper. If it is necessary to reduce any copper oxide formed during the purification of the nitrogen, this c
36、an be done by passing hydrogen through the tube containing the copper, which is heated to 450 C to 500 C. During the reduction process, the water formed is expelled to atmosphere. The tube should be purged with nitrogen before use, the reduced copper emptied from the tube and any agglomerated materi
37、al broken down, and the tube refilled. Alternatively, a commercial source of nitrogen may be employed in the absence of a purification train, provided that the gas in the cylinder contains not more than 30 l of oxygen per litre of nitrogen. In either case, the purified nitrogen shall be passed throu
38、gh a column of magnesium perchlorate (or silica gel) to remove traces of moisture that can be present. BS ISO 5068-2:2007blankBS ISO BSI389 Chiswick High RoadLondonW4 4AL5068-2:2007BSI British Standards InstitutionBSI is the independent national body responsible for preparing British Standards. It p
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