1、Designation: D1412/D1412M 15D1412/D1412M 17Standard Test Method forEquilibrium Moisture of Coal at 96 to 97 Percent RelativeHumidity and 30C30 C1This standard is issued under the fixed designation D1412/D1412M; the number immediately following the designation indicates theyear of original adoption o
2、r, 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. Scope1.1 This test method covers determination of the equilibrium moisture of coal in a
3、n atmosphere over a saturated solution ofpotassium sulfate at 30C.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 ea
4、chsystem 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 i
5、s 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 standardizationestabli
6、shed 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 Practi
8、ce 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 t
9、he bedinherent 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 D330
10、2 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
11、 test 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
12、 and is the direct responsibility of Subcommittee D05.21 on Methods of Analysis.Current edition approved Sept. 1, 2015June 1, 2017. Published September 2015 June 2017. Originally approved in 1956 .1956. Last previous edition approved in 20072015as D1412 07.D1412 15. DOI: 10.1520/D1412_D1412M-15.10.1
13、520/D1412_D1412M-17.2 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 t
14、he standards 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 a
15、ccurately, 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United
16、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 rank coals is required. TheAppendix also provides useful qualit
17、y 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 temperature regulator to maintain a uniform temperature of
18、30.0 C 6 0.2C.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 made for renewing the air (or, ifdesired, dry oxygen-free nitro
19、gen 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.203 mm 8 in. diameter, with 1.18-mm (No. 16)2.36 mm No. 8 openings.4.6 Shaking Mach
20、ine.4.7 DesiccatorDesiccators: Small vacuum-type desiccator, 160 mm in diameter (see Fig. 1).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 (se
21、e Fig. 1).4.7.2 Cooling DesiccatorCabinet-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, cylindr
22、ical, 70 mm in diameter, with well-fitting covers.4.9 Filter Pump, aspirator.4.10 Buchner-Type Funnel, approximately 64 mm 212 in. in diameter.5. Reagents5.1 Dry airDrying AtmospheresAir The atmosphere used to purge the drying oven should be dried to a moisture contentof 1.9 mg/L or less. (Dew point
23、 of -10Cis either dry air or dry nitrogen as specified in 5.1.1 or 5.1.2less.)Any desiccant or dryingmethod capable of achieving this degree of dryness is suitable. .FIG. 1 Vacuum-Type DesiccatorD1412/D1412M 1725.1.1 Dry AirAir with a moisture content of content of 1.9 mgL or less passed through a d
24、rying 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 appropriate desiccants listed in 5.2.5.2 DesiccantsMaterials suitable for use in
25、 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 must be kept fresh enough to assure that the air in the desiccator is dry as def
26、ined 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, and clothing. Magnesium perchlorate is a strong oxidant andcan react violently w
27、ith 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 a manner that attempts to preserve the original sample moisture integrity.6.2 If
28、 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 Take particular care not to overdry low rank coals, especially lignites. Drying w
29、ill 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 oxidized coal.7.1.1 Mine SamplesTake mine samples in accordance with Practice D459
30、6.7.1.2 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 surface moisture of wet coal isto be determined, use the procedure for sampling the
31、 special total moisture subsample described in Practice D2234/D2234M.8. Preparation of Laboratory Samples8.1 Crush the gross sample to No. 4 (4.75-m) a 2.36 mm No. 8 sieve size in accordance with Practice D2013; however, itis important to also observe the technical hazards stated in Section 6 of thi
32、s test method.8.1.1 Divide sample out a 25 g equilibration moisture subsample in accordance with Practice D2013. to be used for testing.8.1.2 Rapidly stage crush the divided sample to pass a No. 16 (1.18-mm) sieve by means of a coffee-mill-type crusher. Thisstage crushing produces a minimum amount o
33、f fine material; however, it increases segregation so the crushed sample shall bethoroughly mixed.8.1.3 Divide out the equilibration moisture subsample to be used for testing.9. Procedure9.1 Place 20 to 25 g of the crushed coal into a 250-mL Erlenmeyer flask and add 100 mL of recently boiled, cooled
34、, distilledwater (Two methods Note 2). Shake the flask mechanically for 30 min, and then place it in the constant-temperature bath for 3 hat 30C. At the end of the wetting period, remove the excess water from the coal by filtering on a Bchner-type funnelapproximately 64 mm 2for preparing the sample
35、for equilibration are provided. The wetted procedure has historically been theprimary method. However, mine samples and certain coals that deteriorate when treated 12 in. in diameter, using suction suppliedby a water filter pump. Use a minimum amount of water to transfer the coal to the filter.After
36、 transfer of the coal, close the funnelwith a rubber stopper fitted with a glass tube through which air saturated with water vapor is passed to prevent drying of the coal.Thoroughly mix the wet coal in the funnel with a spoon and place about 5.0 g in a uniform layer in a weighing bottle of knownweig
37、ht. Place the uncovered weighing bottle in the small vacuum-type desiccator containing a saturated solution of Kwith water,particularly low rank coals (subbituminous C and lignite), may be equilibrated directly without wetting, provided the samples arecollected and prepared with a minimum loss of mo
38、isture. Avoid low 2SO4 for maintaining the relative humidity of 96 to 97 %. Anexcess of crystalline K2SO4 shall extend above the solution level. Evacuate the desiccator to an absolute pressure equivalent toabout 30 mm Hg by means of a mechanical vacuum pump and then totally immerse in a constant-tem
39、perature water bath or placein an insulated air cabinet maintained at 30 6 0.2C for 48 h for all coals higher in rank than lignite. Lignite will require 72 hto reach equilibrium for practical purposes.rank coal samples that have less than their full complement of inherent moisture.NOTE 2Mine samples
40、 and certain coals that deteriorate when treated with water may be equilibrated directly without wetting, provided the samplesD1412/D1412M 173are collected and prepared with a minimum loss of moisture. Unwetted coals should be equilibrated for varying periods of time, in units of 24 h, in orderthat
41、equilibrium may be attained.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 mechanically for 30 min, and then placeit in the constant-temperature
42、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 2 12 in. in diameter, using suction supplied by a water filter pump. Usea minimum amount of water to transfer the coal to the filter.After transfer of
43、the coal, close the funnel with a rubber stopper fittedwith 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 begins to dull or coal particles first begin to disaggregate (particle
44、s 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. Proceed to section 9.2.NOTE 2Over drying the sample during the filtration process to remove excess moisture can result in anomalously low equ
45、ilibrium 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.9.1.2 Unwetted ProcedureThe use of the unwetted procedure for coal samples that
46、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.NOTE 3Moisture desorption and adsorption curves for coal are not entirely reversible.
47、4 The difference or lag between the original and readsorbedmoisture as a function of relative vapor pressure, together with failure to close the hysteresis loop, is termed the “hysteresis effect” and this lag increaseswith decreasing coal rank. The hysteresis effect is believed to be a result of shr
48、inkage due to drying that reduces the coal pore volumes.5 This drying,in turn, decreases moisture holding capacity. Coal samples subjected to partial drying below their full complement of inherent moisture may yieldanomalously low equilibrium moisture values due to this hysteresis effect.9.2 Place t
49、he 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 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. S
