ASTM D2492-02(2007)
(Test Method)Standard Test Method for Forms of Sulfur in Coal
Standard Test Method for Forms of Sulfur in Coal
SIGNIFICANCE AND USE
This test method provides for a separation of coal-associated sulfur into two commonly recognized forms: pyritic and sulfate. Organic sulfur is calculated by difference. Results obtained by the test method are used to serve a number of interests, including the evaluation of coal preparation and processing operations designed to reduce coal sulfur levels.
SCOPE
1.1 This test method applies to the determination of sulfate sulfur and pyritic sulfur in coal and calculates organic sulfur by difference. This test method is not applicable to coke or other carbonaceous materials. Monosulfides (pyrites and FeS2 are disulfides) of iron and elements such as cadmium, lead, vanadium, and zinc can be present in coal. In the range of 0 to 100 ppm, these monosulfides do not contribute significantly to the total inorganic sulfide content.
1.2 The values stated in SI units are to be regarded as standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D2492 − 02(Reapproved 2007)
Standard Test Method for
Forms of Sulfur in Coal
This standard is issued under the fixed designation D2492; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3. Summary of Test Method
3.1 Sulfate Sulfur:
1.1 This test method applies to the determination of sulfate
3.1.1 Sulfate sulfur is extracted from the analysis sample
sulfurandpyriticsulfurincoalandcalculatesorganicsulfurby
difference. This test method is not applicable to coke or other with dilute hydrochloric acid. The sulfate sulfur in the extract
is determined gravimetrically. Sulfates are soluble in hydro-
carbonaceous materials. Monosulfides (pyrites and FeS are
chloric acid, but pyritic and organic sulfur are not.
disulfides) of iron and elements such as cadmium, lead,
vanadium, and zinc can be present in coal. In the range of 0 to
3.2 Pyritic Sulfur:
100 ppm, these monosulfides do not contribute significantly to
3.2.1 Pyritic sulfur is calculated as a stoichiometric combi-
the total inorganic sulfide content.
nation with iron.
3.2.2 Methods:
1.2 The values stated in SI units are to be regarded as
3.2.2.1 Referee Method, which can be used in cases of
standard.
dispute or arbitration. The iron combined in the pyritic state is
1.3 This standard does not purport to address all of the
extracted with dilute nitric acid from the coal residue remain-
safety concerns, if any, associated with its use. It is the
ingaftersulfateextraction(seeNote1).Theironisdetermined
responsibility of the user of this standard to establish appro-
by atomic absorption techniques (see Note 2).
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
NOTE 1—The sulfate extraction step also removes hydrochloric acid
soluble iron (nonpyritic iron) from the test specimen. A test specimen
separate from that used for the sulfate extraction could be used for the
2. Referenced Documents
nitric acid extraction of iron. In this case, both nonpyritic and pyritic iron
areextractedfromthetestspecimen.Sincethereisevidencethatforsome
2.1 ASTM Standards:
coals the extraction of nonpyritic iron by nitric acids falls short of the
D1193Specification for Reagent Water
3,4
amount extracted by hydrochloric acid, the use of a separate test
D2013Practice for Preparing Coal Samples for Analysis
specimen for the nitric acid extraction of iron with subsequent correction
D3173Test Method for Moisture in theAnalysis Sample of
for the contribution of nonpyritic iron is not included in this test method.
Coal and Coke NOTE 2—Round-robin testing of the coal samples used to generate data
for the precision statement in this test method indicates that plasma
D3177TestMethodsforTotalSulfurintheAnalysisSample
emission techniques give results equivalent to those from atomic absorp-
of Coal and Coke
tion analysis for the determination of iron. However, emission analysis is
D3180Practice for Calculating Coal and Coke Analyses
highly susceptible to interferences from other analytes that may be
from As-Determined to Different Bases
dissolved during the extraction of iron. Selection of a wavelength that is
D4239Test Method for Sulfur in the Analysis Sample of free from interferences and linear over the range of iron anticipated for
emissionanalysiscanrequireadetailedcompositionalanalysisofthecoal
Coal and Coke Using High-Temperature Tube Furnace
mineral matter, thus limiting the practicality of this approach.
Combustion
E832Specification for Laboratory Filter Papers 3.2.2.2 Alternative Method, which can be used in routine
practice or when the concerned parties agree on this test
method. The iron originally combined in the pyritic state can
be extracted with dilute hydrochloric acid from the ash
This test method is under the jurisdiction of ASTM Committee D05 on Coal
obtained by incinerating the coal residue remaining after
and Coke and is the direct responsibility of Subcommittee D05.21 on Methods of
Analysis.
Current edition approved May 1, 2007. Published May 2007. Originally
approved in 1966. Last previous edition approved in 2002 as D2492–02. DOI:
10.1520/D2492-02R07. Edwards, A. H., Daybell, G. N., and Pringle, W. J. S., “An Investigation into
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Methods for the Determination of Forms of Sulfur in Coal,” Fuel,Vol 37, 1958, pp.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM 47–59.
Standards volume information, refer to the standard’s Document Summary page on Burns, M. S., “Determination of Pyritic Sulfur inAustralian Coals,” Fuel,Vol
the ASTM website. 49, 1970, pp. 126–33.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2492 − 02 (2007)
sulfateextraction.Theironisdeterminedbyatomicabsorption 6.2.8 Filter Paper—Unless otherwise indicated, references
techniques (see Note 2). to filter paper shall be understood to mean filter paper
conforming to Specification E832.
4. Significance and Use 6.2.9 Hydrochloric Acid,12N (sp. gr. 1.19)—Concentrated
aqueous hydrochloric acid (HCl).
4.1 This test method provides for a separation of coal-
6.2.10 Hydrochloric Acid, 4.8N(2+3)—Mix two volumes
associated sulfur into two commonly recognized forms: pyritic
of concentrated aqueous hydrochloric acid (HCl, sp. gr. 1.19)
and sulfate. Organic sulfur is calculated by difference. Results
with three volumes of water.
obtained by the test method are used to serve a number of
6.2.11 Methyl Orange Indicator Solution, (0.02 g/100
interests, including the evaluation of coal preparation and
mL)—Dissolve 0.02 g of methyl orange in 100 mL of hot
processing operations designed to reduce coal sulfur levels.
water.
6.2.12 Silver Nitrate Solution, (0.43 g/100 mL)—Dissolve
5. Analysis Sample
0.43 g of silver nitrate in 100 mL of water. Store in an amber
5.1 The analysis sample is that sample which has been
glass bottle.
pulverized to pass No. 60 (250-µm) sieve as prepared in
6.3 Procedure:
accordance with Test Method D2013. Moisture shall be deter-
6.3.1 Extraction—Weigh to the nearest 1 mg a 2- to 5-g test
mined in accordance with Test Method D3173 to permit
specimen of analysis sample (see Note 3) and transfer to a
calculations to other than as-analyzed bases.
250-mLErlenmeyerflaskorbeaker.Add50-mLHCl(2+3)in
small increments while stirring to wet the coal thoroughly. A
6. Sulfate Sulfur
few drops of ethanol added to the coal facilitates the wetting
6.1 Apparatus: 1
process. Place on a hotplate and boil gently for ⁄2 h. Carefully
6.1.1 Balance, sensitive to 0.1 mg.
filter the contents into a 400-mLbeaker, using aType II, Class
6.1.2 Crucibles, porcelain, platinum, alundum, or silica of
F filter paper.Wash the filter paper and contents with sufficient
10- to 25-mL capacity for ignition of barium sulfate (BaSO ).
small water washings to ensure the transfer of all HCl extract
6.1.3 Hot Plate, electric or gas-heated with capability for
to the beaker. Save the filter paper with extracted residue for
temperature control.
subsequent extraction of pyrites.
6.1.4 Muffle Furnace, electrically heated and capable of
NOTE 3—It is practical to limit the sample weight to 2 g when the total
regulating the temperature at 800 6 25°C for igniting BaSO .
sulfurlevelis2%orabove,toavoidhandlinganexcessiveamountofiron
in the pyritic extraction.
6.2 Reagents and Materials:
6.2.1 Purity of Reagents—Reagent grade chemicals shall be
6.3.2 Add 5 mLof bromine water to the extract and boil for
used in all tests. Unless otherwise indicated, it is intended that
at least 5 min to oxidize iron and expel excess bromide. Cool
all reagents shall conform to the specifications of the Commit-
to room temperature.
tee onAnalytical Reagents of theAmerican Chemical Society,
6.3.3 Precipitate the iron by slowly adding aqueous ammo-
where such specifications are available. Other grades may be
nium hydroxide (sp. gr. 0.90) until a slight excess is present as
used, provided that the reagent is of sufficiently high purity to
measuredbypHindicatorpaper.Add5mLmorewithconstant
permit its use without lessening the accuracy of the determi-
stirring to coagulate the ferric hydroxide. Filter on a Type II,
nation.
Class E filter paper into a 400-mL or larger beaker. Wash the
6.2.2 Purity of Water—Unless otherwise indicated, refer-
filterpaperseveraltimeswithhotammoniacalsolution(6.2.4).
ences to water shall be understood to mean reagent water
6.3.4 Precipitation—Add two or three drops of methyl
conforming to Specification D1193, Type III.
orange solution and neutralize the filtrate (6.3.3) by cautiously
6.2.3 Ammonium Hydroxide (14.9N, sp. gr. 0.90)—
adding aqueous HCl (sp. gr. 1.19) until the solution turns pink.
concentrated aqueous ammonia.
Add1mLinexcess.Heattoboilingand,whilestirringslowly,
6.2.4 Ammonium Hydroxide Solution 1.5N, (1 + 10)—Mix
add10mLofBaCl solution.Continueboilinggentlyfor10to
one volume of concentrated aqueous ammonia with ten vol-
15minandallowtostandovernightatroomtemperatureorfor
umes of water.
4 h between 70 and 100°C covered with a watch glass. Filter
6.2.5 Barium Chloride Solution (100 g/L)—Dissolve 100 g
through a Type II, Class G filter paper and wash with
of barium chloride (BaCl ·2H O) in water and dilute to 1 L.
2 2
intermittent small washings of hot water until one drop of
6.2.6 Bromine Water(saturated)—Addanexcessofbromine
silver nitrate solution produces no more than a slight opales-
to 1 Lof water. (Warning—Store in a dark bottle and keep in
cence when added to 8 to 10 mL of the filtrate.
a hood.) (Solubility, 42 g/L.)
6.3.5 Sulfate Blank—Prepare a sulfate blank following the
6.2.7 Ethanol, reagent grade, denatured.
same procedure and using the same amounts of all reagents as
described in 6.3.1-6.3.4. Save the filter paper from 6.3.1 of the
blank test for the pyritic iron blank in 7.3.3.
6.3.6 Determination—Preignite crucibles (6.1.2)at800 6
Reagent Chemicals, American Chemical Society Specifications , American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
25°C for 30 min. Cool in a desiccator and weigh to the nearest
listed by the American Chemical Society, see Analar Standards for Laboratory
0.1 mg. Place the specimen filter paper from 6.3.4 and the
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
blank filter paper from 6.3.5 in separate preignited crucibles.
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. Fold the filter papers over loosely to allow free access of air.
D2492 − 02 (2007)
Smokethepaperoffgraduallytopreventspattering.Atnotime 7.3.1 Extraction—Transfer the filter paper and extracted
allow to burn with flame. After the filter paper is practically residue from 6.3.1 to a 250-mL Erlenmeyer flask. Slowly add
consumed, raise the temperature to 800 6 25°C and maintain 50 mL of HNO (1 + 7) with stirring, to ensure complete
for 1 h. Cool the crucibles in a desiccator until equilibrium is wetting and to help disintegrate the filter paper. Either boil
reached. Weigh the crucibles and contents to the nearest 0.1 gently for 30 min or let stand overnight at room temperature.
mg. Ignition is considered to be complete when the weight of Filter the flask and contents through a Type II, Class F filter
the crucible and contents do not change by more than 0.2 mg paper into a 400- to 600-mL beaker. Wash the residue at least
after reheating at 800 6 25°C for 30 min. six times with small increments of water, keeping the total
volume of filtrate between 100 and 200 mL.
6.4 Calculation:
7.3.2 Preparation of Test Solution—Transfer the filtrate
6.4.1 Calculate the percentage of sulfate sulfur as follows:
from 7.3.1 to a 200-mL volumetric flask and dilute to volume
Sulfatesulfur% 5 $@~S 2 C ! 2 ~B 2 C !# 313.735%/W (1)
s B
with water. Transfer a 10-mLaliquot of the diluted filtrate to a
100-mL volumetric flask. Add 10 mL of lanthanum solution
where:
(7.2.8) and dilute to volume with HCl (1 + 49).This is the test
S = weight of sample crucible plus ignited BaSO
solution.
precipitate, g,
7.3.3 Preparation of Blank Test—Perform a parallel blank
C = weight of sample crucible, g,
s
test following the same procedure and reagents as described in
B = weight of blank crucible plus ignited sulfate blank, g,
7.3.1 and 7.3.2 using the filter paper generated in 6.3.1 of the
sulfate blank test.
C = weight of blank crucible, g, and
B
W = weight of test specimen used (6.3.1), g. 7.3.4 Determination of Iron by Atomic Absorption:
7.3.4.1 Spectrometric Conditions—Suitable conditions for
METHODS FOR PYRITIC SULFUR
the determination of iron are as follows:
Wavelength 248.3 nm (0- to 5-ppm Fe)
7. Referee Method—Using Coal Residue Remaining
Wavelength 372.0 nm (5- to 100-ppm Fe)
After Sulfate Extraction
Wavelength 344.1 nm (>100-ppm Fe)
7.1 Apparatus:
Flame: air/acetylene (lean)
7.1.1 Atomic Absorption Spectrophotometer.
7.3.4.2 Preparation of Calibration Solutions—Prepare a set
7.1.2 Balance, see 6.1.1.
of calibration solutions to cover the expected range of concen-
7.1.3 Hot Plate, see 6.1.3.
tration in the test solution (7.3.2) by transferring appropriate
volumes of the iron standard solution (7.2.7) to a series of
7.2 Reagents and Materials:
100-mL volumetric flasks. Add 10 mL of lanthanum solution
7.2.1 Purity of Reagents, see 6.2.1.
(7.2.8). Dilute to the mark with HCl (1 + 49).
7.2.2 Purity of Water, see 6.2.2.
7.3.4.3 Calibration—Measuretheabsorbanceofthecalibra-
7.2.3 Filter Paper, see 6.2.8.
tion solutions (7.3.4.2) using the atomic absorption spectrom-
7.2.4 Hydrochloric Acid,12N (sp. gr. 1.19)—see 6.2.9.
eter (7.1.1) using the appropriate conditions (7.3.4.1). By
7.2.5 Hydrochloric Acid, 4.8N (2 + 3)—see 6.2.10.
regression analysis, construct a calibration curve (see Note 4)
7.2.6 Hydrochloric Acid,0.24N, (1 + 49)—Mix1volumeof
of absorbance against iron content for the calibration solutions
concentratedaqueoushydrochloricacid(HCl,sp.gr.1.19)with
(7.3.4.2).
49 volumes of water.
7.2.7 Iron Standard, (400 ppm)—Weigh 0.4000 g 6 0.1 mg
NOTE 4—For guidance on appropriate procedures for construction of
of clean, pure iron wire or 0.5179 g 6 0.1 mg of high purity calibration curve, see pages 72 to 78 of Wernimont.
iron (III) oxide into a 250-mL beaker. Add 50 mL of HCl
7.3.4.4 Determination of Iron in the Test Solution and Blank
(7.2.5) and cover with a
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