1、Designation: D 1412 07Standard Test Method forEquilibrium Moisture of Coal at 96 to 97 Percent RelativeHumidity and 30C1This standard is issued under the fixed designation D 1412; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers determination of the equilib-rium moisture of coal in an atmosphere over a saturated
3、solution of potassium sulfate at 30C.NOTE 1For information concerning the experimental work on whichthis test method is based, see (1-5).21.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to
4、 address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 121 Ter
5、minology of Coal and CokeD 388 Classification of Coals by RankD 2013 Practice for Preparing Coal Samples for AnalysisD 2234/D 2234M Practice for Collection of a Gross Sampleof CoalD 3172 Practice for Proximate Analysis of Coal and CokeD 3173 Test Method for Moisture in theAnalysis Sample ofCoal and
6、CokeD 3302 Test Method for Total Moisture in CoalD 4596 Practice for Collection of Channel Samples of Coalin a Mine3. Significance and Use3.1 This test method affords a means of estimating the bedmoisture of either coal that is wet and shows visible surfacemoisture or coal that may have lost some mo
7、isture. It may beused for estimating the surface, or extraneous moisture of wetcoal, such moisture being the difference between the totalmoisture as determined by Test Method D 3302 and theequilibrium moisture.3.2 When samples are collected in conformity with Classi-fication D 388, the equilibrium m
8、oisture is considered to beequal to bed moisture with the exception of some low rankcoals that yield equilibrium moisture values below bed mois-ture.3.3 The results obtained by this test method are sensitive tomany influences, and therefore, raw (uncorrected) equilibriummoisture data may be of limit
9、ed value in and of themselves.When working with low rank coals, the results yielded by thistest method require critical assessments. It is recommendedthat the procedure outlined in the Appendix X1 be applied, andthe results corrected before use in situations where a morereliable estimation inherent
10、or bed moisture for low rank coalsis required. The Appendix also provides useful quality assur-ance information which is applicable to coals of all ranks.4. Apparatus4.1 Water Bath or Insulated Air CabinetThe bath orcabinet shall be of sufficient size to accommodate severalvacuum-type desiccators, a
11、nd shall be provided with a tem-perature regulator to maintain a uniform temperature of 30.0 60.2C.4.2 Moisture OvenThe oven shall be so constructed as tohave a uniform temperature in all parts and a minimum of airspace. It may be of the type shown in the Apparatus section ofTest Method D 3173. Prov
12、ision shall be made for renewing theair (or, if desired, dry oxygen-free nitrogen for subbituminousand lignitic coals) in the oven at a rate of two times per minute,with the air dried as defined in 5.1.4.3 Mechanical Vacuum Pump.4.4 Crusher, laboratory, coffee-mill type.4.5 Sieve, 203-mm (8-in.) dia
13、meter, with 1.18-mm (No. 16)openings.4.6 Shaking Machine.4.7 DesiccatorSmall vacuum-type desiccator, 160 mm indiameter (see Fig. 1).4.8 Weighing Bottles, glass, low-form, flat-bottom, cylindri-cal, 70 mm in diameter, with well-fitting covers.1This test method is under the jurisdiction of ASTM Commit
14、tee D05 on Coaland Coke and is the direct responsibility of Subcommittee D05.21 on Methods ofAnalysis.Current edition approved Oct. 1, 2007. Published October 2007. Originallyapproved in 1956 . Last previous edition approved in 2004 as D 1412 04.2The boldface numbers in parentheses refer to a list o
15、f references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Inter
16、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.9 Filter Pump, aspirator.4.10 Buchner-Type Funnel, approximately 64 mm (212 in.)in diameter.5. Reagents5.1 Dry airAir used to purge the drying oven should bedried to a moisture content of 1.9 mg/L or less
17、. (Dew point of-10C or less.) Any desiccant or drying method capable ofachieving this degree of dryness is suitable.5.2 DesiccantsMaterials suitable for use in the desiccatormay 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.
18、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 thatthe air in the desiccator is dry as defined in 5.1. Values inparentheses ( ) are literature values for the residual amount ofmoisture in air at equilibrium with these desiccants. (Wa
19、rning:Sulfuric acid is corrosive and can cause severe damage to eyes,skin, and clothing. Magnesium perchlorate is a strong oxidantand can react violently with organic materials.)6. Technical Hazards6.1 In collecting, containing, handling, reducing, and divid-ing the gross moisture sample, all operat
20、ions must be doneexpeditiously and in a manner that attempts to preserve theoriginal sample moisture integrity.6.2 If the gross sample is too wet to allow reduction anddivision, spread sample in a thin layer and expose to the air ofthe laboratory. Dry no more than necessary to enable satisfac-tory r
21、eduction and division of sample.6.3 Take particular care not to overdry low rank coals,especially lignites. Drying will accelerate oxidation and canalso result in shrinkage of pore size and volume which willaffect the moisture-holding capacity.7. Collection of Gross Samples7.1 Samples shall not be t
22、aken from outcrop, weathered, oroxidized coal.7.1.1 Mine SamplesTake mine samples in accordancewith Practice D 4596.7.1.2 Tipple or Shipment SamplesCollect a representativegross sample of coal in accordance with Practice D 2234/D 2234M. If only the equilibrium moisture is desired, use theGeneral Pur
23、pose Sampling Procedure. If the surface moistureof wet coal is to be determined, use the procedure for samplingthe special total moisture subsample described in PracticeD 2234/D 2234M.8. Preparation of Laboratory Samples8.1 Crush the gross sample to No. 4 (4.75-m) sieve size inaccordance with Practi
24、ce D 2013; however, it is important toalso observe the technical hazards stated in Section 6 of thistest method.8.1.1 Divide sample in accordance with Practice D 2013.8.1.2 Rapidly stage crush the divided sample to pass a No.16 (1.18-mm) sieve by means of a coffee-mill-type crusher.This stage crushi
25、ng produces a minimum amount of finematerial; however, it increases segregation so the crushedsample shall be thoroughly mixed.8.1.3 Divide out the equilibration moisture subsample to beused for testing.9. Procedure9.1 Place 20 to 25 g of the crushed coal into a 250-mLErlenmeyer flask and add 100 mL
26、 of recently boiled, cooled,distilled water (Note 2). Shake the flask mechanically for 30min, and then place it in the constant-temperature bath for 3 hat 30C. At the end of the wetting period, remove the excesswater from the coal by filtering on a Bchner-type funnelapproximately 64 mm (212 in.) in
27、diameter, using suctionsupplied by a water filter pump. Use a minimum amount ofwater to transfer the coal to the filter. After transfer of the coal,close the funnel with a rubber stopper fitted with a glass tubethrough which air saturated with water vapor is passed toprevent drying of the coal. Thor
28、oughly mix the wet coal in thefunnel with a spoon and place about 5.0 g in a uniform layer ina weighing bottle of known weight. Place the uncoveredweighing bottle in the small vacuum-type desiccator containinga saturated solution of K2SO4for maintaining the relativehumidity of 96 to 97 %. An excess
29、of crystalline K2SO4shallextend above the solution level. Evacuate the desiccator to anabsolute pressure equivalent to about 30 mm Hg by means ofa mechanical vacuum pump and then totally immerse in aconstant-temperature water bath or place in an insulated aircabinet maintained at 30 6 0.2C for 48 h
30、for all coals higherin rank than lignite. Lignite will require 72 h to reachequilibrium for practical purposes.NOTE 2Mine samples and certain coals that deteriorate when treatedFIG. 1 Vacuum-Type DesiccatorD1412072with water may be equilibrated directly without wetting, provided thesamples are colle
31、cted and prepared with a minimum loss of moisture.Unwetted coals should be equilibrated for varying periods of time, in unitsof 24 h, in order that equilibrium may be attained.9.2 After equilibration of the coal, restore the pressure in thedesiccator to atmospheric, with the desiccator still in the
32、bath,by slowly admitting dry air for a period of not less than 15 min.Admit the air to the inlet tube of the desiccator after passing itthrough a train consisting first of a bubbler containing H2SO4(sp gr 1.84), then a capillary tube with one end drawn out to atip having a suitable bore for regulati
33、ng the rate of air flow, andfinally a coiled copper tube placed in the constant-temperaturebath. Remove the desiccator from the bath and open immedi-ately. Quickly close the weighing bottle and weigh to thenearest 0.2 mg. Uncover the weighing bottle, place it in themoisture oven preheated to 105C, a
34、nd heat for 112 h. Thenremove the weighing bottle from the oven, cool for 30 min,over one of the desiccants specified in 5.2, in a desiccator, andweigh.10. Calculation10.1 Calculate the percent equilibrium moisture in theanalysis sample as follows:Equilibrium Moisture in Analysis Sample, % 5B2C!B2A!
35、x 100where:A = weight of weighing bottle, grams,B = weight of weighing bottle and wet coal, grams, andC = weight of weighing bottle and dried coal, grams.11. Report11.1 Report the equilibrium or bed moisture to the nearest0.1 % as the percentage loss in weight of the equilibrated coal.12. Precision
36、and Bias12.1 The precision of this test method for the determinationof Equilibrium Moisture in Coal are shown in Table 1.12.1.1 Repeatability Limit (r)The value below which theabsolute difference between two test results of separate andconsecutive test determinations, carried out on the samesample,
37、in the same laboratory, by the same operator, using thesame apparatus on samples taken at random from a singlequantity of homogeneous material, may be expected to occurwith a probability of approximately 95 %.12.1.2 Reproducibility Limit (R)The value below whichthe absolute difference between two te
38、st results carried out indifferent laboratories, using samples taken at random from asingle quantity of material that is as homogeneous as possible,may be expected to occur with a probability of approximately95 %.12.2 BiasCertified standards or absolute methods are notavailable for this test; theref
39、ore, bias of results cannot bedetermined.13. Keywords13.1 bed moisture; coal; equilibrium moisture; extraneousmoisture; surface moistureAPPENDIX(Nonmandatory Information)X1. PRACTICE FOR COMPARING THE RELATIONSHIP BETWEEN INHERENT ANDEQUILIBRIUM MOISTUREX1.1 The purpose of the equilibrium moisture t
40、est is toprovide an estimate of the inherent (bed) moisture. However,evidence has shown that equilibrium moisture results on manylow rank coals, including most lignite coal, are often lowerthan inherent moisture. The procedure described in this appen-dix can be used where there is a question about t
41、he applica-bility of the equilibrium moisture result as an estimator ofinherent moisture. The method is straightforward and hasproven effective in many situations for examining this moisturerelationship.X1.2 Special coal samples, collected at their inherentmoisture level, are analyzed for both total
42、 (inherent) andequilibrium moisture. The results are then compared to see ifdifferences exist between the two moisture parameters, and theend user(s) can then determine whether such differences haveany practical significance. This procedure does not directlyyield inherent moisture values for an enti
43、re coal seam or mine,because the samples are not necessarily representative of thefull seam as would be the case for face channel samples(Practice D 4596). Nevertheless, the procedure does provide atool for evaluating the relationship between inherent andequilibrium moisture for a given area. See (6
44、)X1.3 The most critical step in evaluating this relationship isthe collection of samples containing their full complement ofinherent moisture. Occasionally, it may be difficult to obtain achannel sample that contains no surface moisture. Also, ob-taining a channel sample from thick coal seams, such
45、as thoseTABLE 1 Concentrations Range and Limits for Repeatability andReproducibility of Equilibrium Moisture in CoalRepeatability ReproducibilityRange, Limit, Limit,% rRUnder 5 0.3 0.55to15 0.5 1.0Over 15 1.0 1.5D1412073in the Western United States, is generally impractical, espe-cially from a safet
46、y standpoint. However, the collection offresh, unfractured pieces of coal without visible surface mois-ture is usually feasible. Such samples are considered to containonly inherent moisture (Terminology D 121, ClassificationD 388).NOTE X1.1The collection of coal at its inherent moisture levelsrequir
47、es some degree of judgement, and the sampler should have thenecessary experience. For increased confidence, multiple comparisons arerecommended to define the variability of the data.X1.4 Characteristics and Conditions of SamplingLocalitySamples should be obtained from freshly exposed,unweathered min
48、e faces. Avoid coal that exhibits any signs ofmoisture loss or weathering. There is no single test to deter-mine the degree of weathering of coal under field conditions.However, when an obvious indication of weathering is ob-served, the sample should be obtained from a different localityor sampling
49、postponed until suitable, fresh coal is available.Collecting a substandard sample simply because it was the bestmaterial available will not yield valid results.NOTE X1.2Obvious indicators of weathering include, but are notlimited to: (1) any discoloration of broken coal surfaces or cleats, (2)presence of sulfate minerals resulting from the oxidation of pyrite, (3)presence of gypsum (CaSO4) crystals, and (4) presence of dust, dried,crazed, or fragmented condition of the coal blocks resulting from moistureloss from the coal.A simple field test can be used t
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