1、Designation: D1412/D1412M 17D1412/D1412M 17aStandard Test Method forEquilibrium Moisture of Coal at 96 to 97 Percent RelativeHumidity and 30 C1This standard is issued under the fixed designation D1412/D1412M; the number immediately following the designation indicates theyear of original adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers determination of the equilibrium moisture of coal
3、 in an atmosphere over a saturated solution ofpotassium sulfate at 30 C.NOTE 1For information concerning the experimental work on which this test method is based, see (1-5).21.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in e
4、achsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It
5、is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestabl
6、ished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D121 Terminology of Coal and CokeD388 Classification of Coals by
7、 RankD2013 Practice for Preparing Coal Samples for AnalysisD2234/D2234M Practice for Collection of a Gross Sample of CoalD3172 Practice for Proximate Analysis of Coal and CokeD3173 Test Method for Moisture in the Analysis Sample of Coal and CokeD3302 Test Method for Total Moisture in CoalD4596 Pract
8、ice for Collection of Channel Samples of Coal in a MineE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Significance and Use3.1 This test method affords a means of estimating
9、the inherent moisture of either coal that is wet and shows visible surfacemoisture or coal that may have lost some moisture. It may be used for estimating the surface, or extraneous moisture of wet coal,such moisture being the difference between the total moisture as determined by Test Method D3302
10、and the equilibrium moisture.3.2 When samples are collected in conformity with Classification D388, the equilibrium moisture is considered to be equal tobed moisture with the exception of some low rank coals that yield equilibrium moisture values below bed moisture.3.3 The results obtained by this t
11、est method are sensitive to many influences, and therefore, raw (uncorrected) equilibriummoisture data may be of limited value in and of themselves. When working with low rank coals, the results yielded by this test1 This test method is under the jurisdiction of ASTM Committee D05 on Coal and Coke a
12、nd is the direct responsibility of Subcommittee D05.21 on Methods of Analysis.Current edition approved June 1, 2017Aug. 1, 2017. Published June 2017August 2017. Originally approved in 1956. Last previous edition approved in 20152017 asD1412 15.D1412/D1412M 17. DOI: 10.1520/D1412_D1412M-17.10.1520/D1
13、412_D1412M-17a.2 The boldface numbers in parentheses refer to a list of references at the end of this standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the st
14、andards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accura
15、tely, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor D
16、rive, PO Box C700, West Conshohocken, PA 19428-2959. United States1method require critical assessments. It is recommended that the procedure outlined in the Appendix X1 be applied, and the resultscorrected before use in situations where a more reliable estimation inherent or bed moisture for low ran
17、k coals is required. TheAppendix also provides useful quality assurance information which is applicable to coals of all ranks.4. Apparatus4.1 Water Bath or Insulated Air CabinetThe bath or cabinet shall be of sufficient size to accommodate several vacuum-typedesiccators, and shall be provided with a
18、 temperature regulator to maintain a uniform temperature of 30.0 C 30.0 C 6 0.2 C.4.2 Moisture OvenThe oven shall be so constructed as to have a uniform temperature in all parts and a minimum of air space.It may be of the type shown in the Apparatus section of Test Method D3173. Provision shall be m
19、ade for renewing the air (or, ifdesired, dry oxygen-free nitrogen for subbituminous and lignitic coals) in the oven at a rate of two times per minute, with the airdried as defined in 5.1.4.3 Mechanical Vacuum Pump.4.4 Crusher, laboratory, coffee-mill type.4.5 Sieve, 203 mm 8 in. diameter, with 2.36
20、mm No. 8 openings.4.6 Shaking Machine.4.7 Desiccators:4.7.1 High Vacuum DesiccatorSmall vacuum-type desiccator, approximately 160 mm in diameter, when used in conjunctionwith a saturated K2SO4 solution provides the necessary humidity for the test conditions (see Fig. 1).4.7.2 Cooling DesiccatorCabin
21、et-type desiccator, when used with any of the desiccants (5.2.1 5.2.3) allows the dried testsample to cool to room temperature without substantial regain in mass from adsorption of atmospheric moisture.4.8 Weighing Bottles, glass, low-form, flat-bottom, cylindrical, 70 mm in diameter, with well-fitt
22、ing covers.4.9 Filter Pump, aspirator.4.10 Buchner-Type Funnel, approximately 64 mm 212 in. in diameter.5. Reagents5.1 Drying AtmospheresThe atmosphere used to purge the drying oven is either dry air or dry nitrogen as specified in 5.1.1or 5.1.2.FIG. 1 Vacuum-Type DesiccatorD1412/D1412M 17a25.1.1 Dr
23、y AirAir with a moisture content of content of 1.9 mgL or less passed through a drying column containing any ofthe appropriate desiccants listed in 5.2.5.1.2 Dry NitrogenCompressed nitrogen gas certified having an oxygen content less than 30 L/Land passed through a dryingcolumn containing any of the
24、 appropriate desiccants listed in 5.2.5.2 DesiccantsMaterials suitable for use in the desiccator may be chosen from the following:5.2.1 Anhydrous Calcium Sulfate (0.004 mg/L).5.2.2 Silica Gel.5.2.3 Magnesium Perchlorate (0.0005 mg/L).5.2.4 Sulfuric Acid, Concentrated (0.003 mg/L).5.2.5 The desiccant
25、 must be kept fresh enough to assure that the air in the desiccator is dry as defined in 5.1. Values inparentheses ( ) are literature values for the residual amount of moisture in air at equilibrium with these desiccants. (Warning:Sulfuric acid is corrosive and can cause severe damage to eyes, skin,
26、 and clothing. Magnesium perchlorate is a strong oxidant andcan react violently with organic materials.)5.3 K2SO4Crystalline Potassium Sulfate6. Technical Hazards6.1 In collecting, containing, handling, reducing, and dividing the gross moisture sample, all operations must be doneexpeditiously and in
27、 a manner that attempts to preserve the original sample moisture integrity.6.2 If the gross sample is too wet to allow reduction and division, spread sample in a thin layer and expose to the air of thelaboratory. Dry no more than necessary to enable satisfactory reduction and division of sample.6.3
28、Take particular care not to overdry low rank coals, especially lignites. Drying will accelerate oxidation and can also resultin shrinkage of pore size and volume which will affect the moisture-holding capacity.7. Collection of Gross Samples7.1 Samples shall not be taken from outcrop, weathered, or o
29、xidized coal.7.1.1 Mine SamplesTake mine samples in accordance with Practice D4596.7.1.2 Tipple or Shipment SamplesCollect a representative gross sample of coal in accordance with Practice D2234/D2234M.If only the equilibrium moisture is desired, use the General Purpose Sampling Procedure. If the su
30、rface moisture of wet coal isto be determined, use the procedure for sampling the special total moisture subsample described in Practice D2234/D2234M.8. Preparation of Laboratory Samples8.1 Crush the sample to a 2.36 mm No. 8 sieve size in accordance with Practice D2013; however, it is important to
31、alsoobserve the technical hazards stated in Section 6 of this test method.8.1.1 Divide out a 25 g equilibration moisture subsample in accordance with Practice D2013 to be used for testing.9. Procedure9.1 Two methods for preparing the sample for equilibration are provided. The wetted procedure has hi
32、storically been theprimary method. However, mine samples and certain coals that deteriorate when treated with water, particularly low rank coals(subbituminous C and lignite), may be equilibrated directly without wetting, provided the samples are collected and prepared witha minimum loss of moisture.
33、 Avoid low rank coal samples that have less than their full complement of inherent moisture.9.1.1 Wetted ProcedurePlace the 25 g sub-split equilibration sample coal into a 250 mL Erlenmeyer flask and addapproximately 100 mL of recently boiled, cooled, distilled water (Note 2). Shake the flask mechan
34、ically for 30 min, and then placeit in the constant-temperature bath for 3 h at 30 C. At the end of the wetting period, remove the excess water from the coal byfiltering on a Bchnertype funnel approximately 64 mm 64 mm 2 12 in. in diameter, using suction supplied by a water filter pump.Use a minimum
35、 amount of water to transfer the coal to the filter. After transfer of the coal, close the funnel with a rubber stopperfitted with a glass tube through which air saturated with water vapor is passed to prevent drying of the coal (Note 2). Cease filtrationas soon as the wet sheen on particle surfaces
36、 begins to dull or coal particles first begin to disaggregate (particles stop clingingtogether). Thoroughly mix the wet coal in the funnel with a spoon and place about 5.0 g in a uniform layer in a weighing bottleof known weight.mass. Proceed to section 9.2.NOTE 2Over drying the sample during the fi
37、ltration process to remove excess moisture can result in anomalously low equilibrium moisture values.Conversely, stopping the filtration prematurely may leave the sample too wet. In the latter case, the sample may not reach equilibrium in the desiccatorwithin the prescribed equilibration period.9.1.
38、2 Unwetted ProcedureThe use of the unwetted procedure for coal samples that have sustained partial drying is notrecommended due to the hysteresis effect (Note 3). Place about 5.0 g of the crushed gross sample coal in a uniform layer in aweighing bottle of known mass. Proceed to section 9.2.D1412/D14
39、12M 17a3NOTE 3Moisture desorption and adsorption curves for coal are not entirely reversible.4 The difference or lag between the original and readsorbedmoisture as a function of relative vapor pressure, together with at the maximum relative vapor pressure is due to a failure to close the hysteresis
40、loop,and is often termed the “hysteresis effect” and this lag effect.” The effect increases with decreasing coal rank. The hysteresis effect rank and is believedto be a result of shrinkage due to drying that reduces the coal pore volumes.volume,5 This drying, which, in turn, decreases moisture holdi
41、ng capacity.Coal Because of this effect, coal samples subjected to partial drying below their full complement of inherent moisture moisture, or samples of low rankcoals (which have large pore sizes) may yield anomalously low equilibrium moisture values due to this hysteresis effect.values.9.2 Place
42、the uncovered weighing bottle in the small vacuum-type desiccator containing a saturated solution of K2SO4 formaintaining the relative humidity of 96 % to 97 %.An excess of crystalline K2SO4 shall extend above the solution level. Evacuatethe desiccator to an absolute pressure equivalent to about 30
43、mm Hg by means of a mechanical vacuum pump and then totallyimmerse in a constant-temperature water bath or place in an insulated air cabinet maintained at 30 C 6 0.2 C for 48 h for allcoals higher in rank than subbituminous C. Subbituminous C and lignite coal will require 72 h to reach equilibrium f
44、or practicalpurposes.9.3 After equilibration of the coal, restore the pressure in the desiccator to atmospheric, with the desiccator still in the bath, byslowly admitting dry air for a period of not less than 15 min.Admit the air to the inlet tube of the desiccator after passing it througha train co
45、nsisting first of a bubbler containing H2SO4 (sp gr 1.84), then a capillary tube with one end drawn out to a tip havinga suitable bore for regulating the rate of air flow, and finally a coiled copper tube placed in the constant-temperature bath. Removethe desiccator from the bath and open immediatel
46、y. Quickly close the weighing bottle and weigh to the nearest 0.1 mg. Uncoverthe weighing bottle, place it in the moisture oven preheated to 105 C, through which passes a current of dry air or nitrogen per5.1, and heat for 112 h. Then remove the weighing bottle from the oven, cool for 30 min, over o
47、ne of the desiccants specified in5.2, in a desiccator, and weigh.10. Calculation10.1 Calculate the percent equilibrium moisture in the analysis sample as follows:Equilibrium Moisture in Analysis Sample,%5B 2C!B2A! x 100where:A = mass of weighing bottle, grams,B = mass of weighing bottle and wet coal
48、, grams, andC = mass of weighing bottle and dried coal, grams.11. Report11.1 Report the equilibrium or bed moisture to the nearest 0.1 % as the percentage loss in mass of the equilibrated coal.12. Precision and Bias12.1 The precision of this test method is based on an interlaboratory study of ASTM D
49、1412, Standard Test Method forEquilibrium Moisture of Coal at 96 % to 97 % Percent Relative Humidity and 30 C, conducted in 2011.Atotal of 14 laboratoriesparticipated in this study, testing 9nine coal samples (3(three each of bituminous, subbituminous; and lignite ranks); and usingeither air or nitrogen as the drying atmosphere. Each of the total 796 “test results” reported represents an individual determinationand all participants were asked to report duplicate test results. Except for those analyses with fewer than 6six laborator
