1、Designation: D 4326 04Standard Test Method forMajor and Minor Elements in Coal and Coke Ash By X-RayFluorescence1This standard is issued under the fixed designation D 4326; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f 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.NoteSection 13 Precision and Bias, was corrected and the year date was changed on May 26, 2004.1. Scope1.1 This test method cov
3、ers the analysis of the commonlydetermined major and minor elements in ash from coal or cokeusing X-ray fluorescence (XRF) techniques.NOTE 1Test Method D 1757 is used for determination of sulfur.NOTE 2Although not included in the present method, the determina-tion of barium, strontium, and manganese
4、 may be required to yieldadequate totals.1.2 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 address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
5、he 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:2D 1757 Test Methods for Sulfur in Ash from Coal and CokeD 3174 Test Method for Ash in the Analysis Sample
6、of Coaland Coke from CoalE 2 Methods of Preparation of Micrographs of Metals andAlloys (Including Recommended Practice for Photographyas Applied to Metallography)3E 11 Specification for Wire-Cloth Sieves for Testing Pur-poses3. Summary of Test Method3.1 The coal or coke to be analyzed is ashed under
7、 standardconditions and ignited to constant weight. Previously ashedmaterials are ignited to constant weight under standard condi-tions. The ash is fused with lithium tetraborate (Li2B4O7)orother suitable flux and either ground and pressed into a pelletor cast into a glass disk. The pellet or disk i
8、s then irradiated byan X-ray beam of short wavelength (high energy). The char-acteristic X-rays of the atom that are emitted or fluorescedupon absorption of the primary or incident X-rays are dispersedand intensities at selected wavelengths are measured by sensi-tive detectors. Detector output is re
9、lated to concentration bycalibration curves or by computerized data-handling equip-ment.3.2 The K spectral lines are used for all of the elementsdetermined by this procedure.3.3 All elements are determined as the element and reportedas the oxide and include Si, Al, Fe, Ca, Mg, Na, K, P, Ti, Mn,Sr, a
10、nd Ba.4. Significance and Use4.1 A compositional analysis of ash is used in describing thequality of coal for its complete characterization. Ash compo-sition is useful in predicting slagging and fouling characteris-tics of combusted materials as well as the potential utilizationof ash by-products.4.
11、2 The chemical composition of laboratory prepared coalor coke ash is rarely, if ever, representative of the compositionof the mineral matter in the coal because the ashing process canalter some minerals. However, it can approximate the compo-sition of the fly ash and slag resulting from commercialco
12、mbustion of coal or coke.5. Apparatus5.1 Ashing Furnace, with air circulation as specified in TestMethod D 3174 and capable of having its temperature regu-lated between 700 and 750C.5.2 Fusion Furnace or Fluxing Device, with an operatingtemperature of at least 1000C.5.3 Fusion Crucibles, either high
13、-purity graphite (22 mmhigh and 19 mm wide, inside diameter) or platinum-gold alloyof a similar or larger capacity.5.4 Pulverizers, including agate, mullite or tungsten carbidemortar, and pestle, minimum capacity 25 mL.1This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke
14、 and is the direct responsibility of Subcommittee D05.29 on MajorElements in Ash and Trace Elements of Coal.Current edition approved May 26, 2004. Published June 2004. Originallyapproved in 1984. Last previous edition approved 2003 as D 4326 03.2Annual Book of ASTM Standards, Vol 05.05.For reference
15、d 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.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C70
16、0, West Conshohocken, PA 19428-2959, United States.5.5 Sieves, 250-m (No. 60) and 75-m (No. 200) U.S.Astandard sieve as specified in Specification E 11.5.6 CompactorA press equipped with a gage enablingreproducible pressures (exceeding 1.72 3 108Pa (25 000 psi)if pressed pellets are utilized.5.7 Exc
17、itation Source, with a stable electrical power supply(61 %) and a high-intensity, short-wavelength X-ray capabil-ity.5.8 SpectrometerA wavelength or energy dispersive sys-tem equipped with a vacuum sample chamber.5.8.1 Analyzing Crystal (Wavelength Units)The choice ofthe analyzing crystal is made on
18、 the basis of the element to bedetermined. An attempt should be made to use the crystal thatyields the maximum sensitivity with minimum interferences.The same crystal must be used for standards and unknowns.5.8.2 DetectorsScintillation and gas-flow counters areused with wavelength systems while lith
19、ium-drifted diodes areused for energy dispersive systems.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemic
20、al Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Detector GasThe usual gas composition of the gasused in the flow-propo
21、rtional counters is 90 % argon, 10 %methane, although other compositions may be used.6.3 Heavy AbsorberWhere heavy absorbers, such as lan-thanum oxide or barium oxide, are used they shall be aminimum of 99.99 % purity.6.4 FluxesLithium or sodium borates or carbonates, orcombination thereof, are ofte
22、n used for sample fusion. Lithiumor ammonium iodide used as a nonwetting agent and potassiumor ammonium nitrate used as an oxidizing agent may be usedprovided they do not contribute to spectral interference.6.5 BindersWhere pressed pellets are used for analysis,the binder used shall contribute no sp
23、ectral interferences duringthe determination.7. Preparation of Coal Ash and Coke Ash7.1 Prepare the ash from a thoroughly mixed representativeanalysis sample of air-dried coal or coke that has been groundto pass a 250-m (No. 60) U.S.A standard sieve. Spread thecoal or coke in a layer not over 6 mm (
24、14 in.) in depth in afireclay, porcelain, or platinum roasting dish. Place the ash in acold muffle furnace and heat gradually so that the temperaturereaches 500C in 1 h and 750C in 2 h. Ignite at 750C toconstant weight, cool, grind to pass a 74-m (No. 200) U.S.Astandard sieve, and reignite at 750C f
25、or 1 h. Immediately,prepare the analysis sample or store the dry ash in a vacuumdesiccator. If samples are stored and the absorption of moistureor CO2, or both, is in question, reignite the ash using the500-750C staged combustion before use. Alternatively, deter-mine loss on ignition using the 500-7
26、50C staged combustionon a separate sample weighed out at the same time as the testportion and make the necessary corrections. Thoroughly mixeach sample before weighing.7.2 Materials previously ashed, fly ash, or bottom ash mustbe ignited to constant weight at 750C and cooled in adesiccator before an
27、alysis sample preparation, or alternatively,weight loss or gain must be determined on a second sample at750C taken at the same time as the analysis sample so thatanalysis determined on an as-received basis can be reported onan ignited ash basis.8. Preparation of Analytical Sample8.1 Mix the powdered
28、 sample, weigh a portion of thesample, and mix with a suitable amount of flux (2 to 10 g offlux per gram of sample) (Note 3). When a heavy absorber isused (Note 4), it is added at this point in an amount equal to theamount of sample and thoroughly blended with the mix. Aportion of the flux used as a
29、 cap on the mix ensures washingdown any of the material from the sides of the crucible.NOTE 3The amount of sample and flux used are determined by thenecessity of forming a disk or pellet of 2-mm thickness to fit the sampleholder of the spectrometer used. All fluxes and other additives should beadded
30、 in an appropriate manner at the time of sample preparation.8.1.1 Fluxing materials commonly available are not consis-tent and can vary in volatile losses upon fusing. In order toeliminate errors caused by this loss, one of three methods mustbe employed. First, the entire bottle of flux may be heate
31、d tothe fused state, then cooled, reground, and stored in a desic-cator. Second, a weighed sample from each bottle is fused anda loss on fusion is determined, which is then applied as acorrection for each sample prepared from that bottle. Third, theentire mass of each sample prepared (flux, sample,
32、and heavyabsorber, if used) may be weighed and an independent fusionloss calculated.NOTE 4Use of a heavy absorber has the advantage of allowing the useof a much smaller sample weight to reach infinite thickness and allows forcalculation of concentrations using a simple linear regression coefficient.
33、It does, however, prevent determination of a number of trace elements andmay be impractical for energy dispersive systems where its addition maycause increased detector dead time and complicate correction procedures.The use of a heavy absorber is recommended only when its absence isimpractical or in
34、convenient.8.2 The sample mix is fused at approximately 1000C, in afusion furnace of fluxing device, for a length of time sufficientto guarantee complete dissolution of the sample. Some type ofagitation of the crucible, such as swirling or shaking, must beused in order to ensure a uniform melt.8.3 T
35、he fusion melt will then be made into a suitable mountby casting the liquid into a mold and forming a glass disk or byallowing the pellet to cool, grinding to a fine powder with 2 %of a plasticizer or binder, and pressing into a pellet at aminimum of 1.72 3 108Pa (25 000-lbs/in2) pressure with asuit
36、able backing as added support.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., an
37、d the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D43260428.4 The glass disk must be cooled at a rate that is fastenough to prevent any segregation occurring and, at the sametime, slowly enough to prevent stresses that will crack thegla
38、ss. Cracked glass disks may be refused and recast withoutloss of precision.8.5 Whichever method of preparation of the analyticalmount is used, it is essential that a smooth, uniform, and flatsurface is exposed to the exciting radiation.8.6 It is essential that the entire sample preparation proce-dur
39、e (including sample weight, flux weight and ratio, grinding,casting, and so forth) be followed precisely for all analyticalmounts and standards. Even a small change in the selectedprocedures will require remaking of all standards to match thechanged procedure. All calibration standards and the unkno
40、wnsto be used with them must be prepared in exactly the samemanner with all weighings to be made to the nearest 1 mg.9. Preparation of XRF Spectrometer9.1 Follow the manufacturers instruction for the initialassembly, conditioning, and preparation of the XRF unit.9.2 Follow the manufacturers instruct
41、ions with respect tocontrol setting and operation.10. Excitation and Exposure10.1 Position the sample in the chamber provided for thispurpose. Avoid touching or otherwise contaminating thesample surface. Produce and record the spectrum at the settingsrecommended for the instrument. Prepare and analy
42、ze dupli-cate mounts for all samples with duplicate readings on eachmount. For in-house laboratories, single determinations may beperformed as long as the precision and bias limits are met.11. Safety Precautions11.1 It is necessary to obtain training before using X-rayfluorescence equipment and impo
43、rtant to understand com-pletely the operation of the instrument to ensure that theprovisions of 1.3 are met.12. Calculations and Calibration12.1 Standards for calibration may be prepared from stan-dard reference materials or synthetically blended pure com-pounds. It is required that the range of con
44、centrations repre-sented by the standards exceeds that of any unknown.12.2 Calculation of elemental concentrations may be ac-complished by empirical fundamental parameter or linearregression in accordance with Practice E 2.13. Precision and Bias513.1 PrecisionThe relative precision of this test meth
45、odfor the determination of major and minor elements in coal andcoke ash was calculated from data obtained from ashes with theconcentration ranges shown in Table 1.NOTE 5Data were also collected for MnO2,SO3, SrO, and BaO in theround robin used to generate the data for calculating the repeatability a
46、ndreproducibility intervals or limits for the first nine elemental oxides inTable 1. These data were used to calculate the repeatability and reproduc-ibility intervals or limits for the last four elemental oxides in the table. Theanalyses of MnO2,SO3, SrO, and BaO were not included in the originalsc
47、ope and responsibility of the Task Group and are listed for informationalpurposes only.13.1.1 Repeatability the value below which the absolutedifference between two test results of separate and consecutivetest determinations, carried out on the same sample in the samelaboratory by the same operator
48、using the same apparatus onsamples taken at random from a single quantity of homoge-neous material, may be expected to occur with a probability ofapproximately 95%.13.1.2 Reproducibilitythe value below which the absolutedifference between two test results carried out in differentlaboratories using s
49、amples taken at random from a singlequantity of material that is as homogeneous as possible, may beexpected to occur with a probability of approximately 95%.TABLE 1 Concentration Ranges and Intervals or Limits forRepeatability and Reproducibility for Major and MinorElemental Oxides in Coal and Coke AshElemental OxidePercent, by Weight, of Moisture-Free AshConcentrationRangeRepeatability,I(r)AReproducibility,I(R)ASiO233.257.5 1.26 4.39Al2O311.633.1 0.83 0.51 + 0.10(x)Fe2O33.141.8 0.21 + 0.005(x) 0.99 + 0.035(x)CaO 1.525.2 0.16 + 0.01(x) 0.22 + 0
