ASTM D2492-90(1998)
(Test Method)Standard Test Method for Forms of Sulfur in Coal
Standard Test Method for Forms of Sulfur in Coal
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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Standards Content (Sample)
Designation: D 2492 – 90 (Reapproved 1998)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Forms of Sulfur in Coal
This standard is issued under the fixed designation D 2492; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Pyritic Sulfur:
3.2.1 Pyritic sulfur is calculated as a stoichiometric combi-
1.1 This test method applies to the determination of sulfate
nation with iron.
sulfur and pyritic sulfur in coal and calculates organic sulfur by
3.2.2 Methods:
difference. This test method is not applicable to coke or other
3.2.2.1 Referee Method, which can be used in cases of
carbonaceous materials. Monosulfides (pyrites and FeS are
dispute or arbitration. The iron combined in the pyritic state is
disulfides) of iron and elements such as cadmium, lead,
extracted with dilute nitric acid from the coal residue remain-
vanadium, and zinc can be present in coal. In the range of 0 to
ing after sulfate extraction (Note 1). The iron is determined by
100 ppm, these monosulfides do not contribute significantly to
atomic absorption techniques (Note 2).
the total inorganic sulfide content.
1.2 The values stated in SI units are to be regarded as
NOTE 1—The sulfate extraction step also removes hydrochloric acid
standard. soluble iron (nonpyritic iron) from the test specimen. A test specimen
separate from that used for the sulfate extraction could be used for the
1.3 This standard does not purport to address all of the
nitric acid extraction of iron. In this case, both nonpyritic and pyritic iron
safety concerns, if any, associated with its use. It is the
are extracted from the test specimen. Since there is evidence that for some
responsibility of the user of this standard to establish appro-
coals the extraction of nonpyritic iron by nitric acids falls short of the
priate safety and health practices and determine the applica-
5,6
amount extracted by hydrochloric acid, the use of a separate test
bility of regulatory limitations prior to use.
specimen for the nitric acid extraction of iron with subsequent correction
for the contribution of nonpyritic iron is not included in this test method.
2. Referenced Documents
NOTE 2—Round-robin testing of the coal samples used to generate data
for the precision statement in this test method indicates that plasma
2.1 ASTM Standards:
emission techniques give results equivalent to those from atomic absorp-
D 1193 Specification for Reagent Water
3 tion analysis for the determination of iron. However, emission analysis is
D 2013 Method of Preparing Coal Samples for Analysis
highly susceptible to interferences from other analytes that may be
D 3173 Test Method for Moisture in the Analysis Sample of
dissolved during the extraction of iron. Selection of a wavelength that is
Coal and Coke
free from interferences and linear over the range of iron anticipated for
D 3177 Test Methods for Total Sulfur in the Analysis
emission analysis can require a detailed compositional analysis of the coal
Sample of Coal and Coke mineral matter, thus limiting the practicality of this approach.
D 3180 Practice for Calculating Coal and Coke Analyses
3.2.2.2 Alternative Method, which can be used in routine
from As-Determined to Different Bases
practice or when the concerned parties agree on this test
D 4239 Test Methods for Sulfur in the Analysis Sample of
method. The iron originally combined in the pyritic state can
Coal and Coke Using High-Temperature Tube Furnace
be extracted with dilute hydrochloric acid from the ash
Combustion Methods
obtained by incinerating the coal residue remaining after
E 832 Specification for Laboratory Filter Papers
sulfate extraction. The iron is determined by atomic absorption
techniques (Note 2).
3. Summary of Test Method
3.1 Sulfate Sulfur: 4. Significance and Use
3.1.1 Sulfate sulfur is extracted from the analysis sample
4.1 This test method provides for a separation of coal-
with dilute hydrochloric acid. The sulfate sulfur in the extract
associated sulfur into two commonly recognized forms: pyritic
is determined gravimetrically. Sulfates are soluble in hydro-
and sulfate. Organic sulfur is calculated by difference. Results
chloric acid, but pyritic and organic sulfur are not.
obtained by the test method are used to serve a number of
interests, including the evaluation of coal preparation and
This test method is under the jurisdiction of ASTM Committee D-5 on Coal and processing operations designed to reduce coal sulfur levels.
Coke and is the direct responsibility of Subcommittee D05.21 on Methods of
Analysis.
Current edition approved March 30, 1990. Published May 1990. Originally Edwards, A. H., Daybell, G. N., and Pringle, W. J. S., “An Investigation into
published as D 2492 – 66 T. Last previous edition D 2492 – 84. Methods for the Determination of Forms of Sulfur in Coal,” Fuel, Vol 37, 1958, pp.
Annual Book of ASTM Standards, Vol 11.01. 47–59.
3 6
Annual Book of ASTM Standards, Vol 05.05. Burns, M. S., “Determination of Pyritic Sulfur in Australian Coals,” Fuel,Vol
Annual Book of ASTM Standards, Vol 14.04. 49, 1970, pp. 126–33.
D 2492
5. Analysis Sample 6.3 Procedure:
6.3.1 Extraction—Weigh to the nearest 1 mg a 2- to 5-g test
5.1 The analysis sample is that sample which has been
specimen of analysis sample (Note 3) and transfer to a 250-mL
pulverized to pass No. 60 (250-μm) sieve as prepared in
Erlenmeyer flask or beaker. Add 50-mL HCl (2 + 3) in small
accordance with Test Method D 2013. Moisture shall be
increments while stirring to wet the coal thoroughly. A few
determined in accordance with Test Method D 3173 to permit
drops of ethanol added to the coal facilitates the wetting
calculations to other than as-analyzed bases.
process. Place on a hotplate and boil gently for ⁄2 h. Carefully
6. Sulfate Sulfur
filter the contents into a 400-mL beaker, using a Type II, Class
6.1 Apparatus:
F filter paper. Wash the filter paper and contents with sufficient
6.1.1 Balance, sensitive to 0.1 mg.
small water washings to ensure the transfer of all HCl extract
6.1.2 Crucibles, porcelain, platinum, alundum, or silica of
to the beaker. Save the filter paper with extracted residue for
10- to 25-mL capacity for ignition of barium sulfate (BaSO ).
4 subsequent extraction of pyrites.
6.1.3 Hot Plate, electric or gas-heated with capability for
NOTE 3—It is practical to limit the sample weight to 2 g when the total
temperature control.
sulfur level is 2 % or above, to avoid handling an excessive amount of iron
6.1.4 Muffle Furnace, electrically heated and capable of
in the pyritic extraction.
regulating the temperature at 800 6 25°C for igniting BaSO .
6.3.2 Add 5 mL of bromine water to the extract and boil for
6.2 Reagents and Materials:
at least 5 min to oxidize iron and expel excess bromide. Cool
6.2.1 Purity of Reagents—Reagent grade chemicals shall be
to room temperature.
used in all tests. Unless otherwise indicated, it is intended that
all reagents shall conform to the specifications of the Commit-
6.3.3 Precipitate the iron by slowly adding aqueous ammo-
tee on Analytical Reagents of the American Chemical Society, nium hydroxide (sp. gr. 0.90) until a slight excess is present as
where such specifications are available. Other grades may be
measured by pH indicator paper. Add 5 mL more with constant
used, provided that the reagent is of sufficiently high purity to stirring to coagulate the ferric hydroxide. Filter on a Type II,
permit its use without lessening the accuracy of the determi- Class E filter paper into a 400-mL or larger beaker. Wash the
nation. filter paper several times with hot ammoniacal solution (6.2.4).
6.2.2 Purity of Water—Unless otherwise indicated, refer-
6.3.4 Precipitation—Add two or three drops of methyl
ences to water shall be understood to mean reagent water
orange solution and neutralize the filtrate (6.3.3) by cautiously
conforming to Specification D 1193, Type III.
adding aqueous HCl (sp. gr. 1.19) until the solution turns pink.
6.2.3 Ammonium Hydroxide (14.9N, sp. gr. 0.90)—
Add 1 mL in excess. Heat to boiling and, while stirring slowly,
concentrated aqueous ammonia.
add 10 mL of BaCl solution. Continue boiling gently for 10 to
6.2.4 Ammonium Hydroxide Solution 1.5N, (1 + 10)—Mix
15 min and allow to stand overnight at room temperature or for
one volume of concentrated aqueous ammonia with ten vol-
4 h between 70 and 100°C covered with a watch glass. Filter
umes of water.
through a Type II, Class G filter paper and wash with
6.2.5 Barium Chloride Solution (100 g/L)—Dissolve 100 g
intermittent small washings of hot water until one drop of
of barium chloride (BaCl ·2H O) in water and dilute to 1 L.
silver nitrate solution produces no more than a slight opales-
2 2
6.2.6 Bromine Water (saturated)—Add an excess of bro-
cence when added to 8 to 10 mL of the filtrate.
mine to 1 L of water. (Caution—Store in a dark bottle and
6.3.5 Sulfate Blank—Prepare a sulfate blank following the
keep in a hood.) (Solubility, 42 g/L.)
same procedure and using the same amounts of all reagents as
6.2.7 Ethanol, reagent grade, denatured.
described in 6.3.1-6.3.4. Save the filter paper from 6.3.1 of the
6.2.8 Filter Paper—Unless otherwise indicated, references
blank test for the pyritic iron blank in 7.3.3.
to filter paper shall be understood to mean filter paper
6.3.6 Determination—Preignite crucibles (6.1.2) at 800 6
conforming to Specification E 832.
25°C for 30 min. Cool in a desiccator and weigh to the nearest
6.2.9 Hydrochloric Acid,12N (sp. gr. 1.19)—Concentrated
0.1 mg. Place the specimen filter paper from 6.3.4 and the
aqueous hydrochloric acid (HCl).
blank filter paper from 6.3.5 in separate preignited crucibles.
6.2.10 Hydrochloric Acid, 4.8N (2 + 3)—Mix two volumes
Fold the filter papers over loosely to allow free access of air.
of concentrated aqueous hydrochloric acid (HCl, sp. gr. 1.19)
Smoke the paper off gradually to prevent spattering. At no time
with three volumes of water.
allow to burn with flame. After the filter paper is practically
6.2.11 Methyl Orange Indicator Solution, (0.02 g/100
consumed, raise the temperature to 800 6 25°C and maintain
mL)—Dissolve 0.02 g of methyl orange in 100 mL of hot
for 1 h. Cool the crucibles in a desiccator until equilibrium is
water.
reached. Weigh the crucibles and contents to the nearest 0.1
6.2.12 Silver Nitrate Solution, (0.43 g/100 mL)—Dissolve
mg. Ignition is considered to be complete when the weight of
0.43 g of silver nitrate in 100 mL of water. Store in an amber
the crucible and contents do not change by more than 0.2 mg
glass bottle.
after reheating at 800 6 25°C for 30 min.
6.4 Calculation:
Reagent Chemicals, American Chemical Society Specifications, American
6.4.1 Calculate the percentage of sulfate sulfur as follows:
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
Sulfate sulfur % 5 @~S 2 C ! 2 ~B 2 C !# 3 13.735 /W (1)
$ %
s B
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
where:
MD.
D 2492
7.3.3 Preparation of Blank Test—Perform a parallel blank
S 5 weight of sample crucible plus ignited BaSO pre-
test following the same procedure and reagents as described in
cipitate, g;
7.3.1 and 7.3.2 using the filter paper generated in 6.3.1 of the
C 5 weight of sample crucible, g;
s
B 5 weight of blank crucible plus ignited sulfate blank, g, sulfate blank test.
C 5 weight of blank crucible, g; and, 7.3.4 Determination of Iron by Atomic Absorption:
B
W 5 weight of test specimen used (6.3.1), g.
7.3.4.1 Spectrometric Conditions—Suitable conditions for
the determination of iron are as follows:
METHODS FOR PYRITIC SULFUR
Wavelength 248.3 nm (0- to 5-ppm Fe)
Wavelength 372.0 nm (5- to 100-ppm Fe)
7. Referee Method—Using Coal Residue Remaining
Wavelength 344.1 nm (>100-ppm Fe)
After Sulfate Extraction
Flame: air/acetylene (lean)
7.1 Apparatus:
7.3.4.2 Preparation of Calibration Solutions—Prepare a set
7.1.1 Atomic Absorption Spectrophotometer.
of calibration solutions to cover the expected range of concen-
7.1.2 Balance, see 6.1.1.
tration in the test solution (7.3.2) by transferring appropriate
7.1.3 Hot Plate, see 6.1.3.
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—Measure the absorbance of the cali-
7.2.3 Filter Paper, see 6.2.8.
bration solutions (7.3.4.2) using the atomic absorption spec-
7.2.4 Hydrochloric Acid,12N (sp. gr. 1.19)—see 6.2.9.
trometer (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 (Note 4) of
7.2.6 Hydrochloric Acid, 0.24N, (1 + 49)—Mix 1 volume of
absorbance against iron content for the calibration solutions
concentrated aqueous hydrochloric acid (HCl, sp. gr. 1.19) with
(7.3.4.2).
49 volumes of water.
NOTE 4—For guidance on appropriate procedures for construction of
7.2.7 Iron Standard, (400 ppm)—Weigh 0.4000 g 6 0.1 mg
calibration curve, see pages 72 to 78 of Wernimont.
of clean, pure iron wire or 0.5179 g 6 0.1 mg of high purity
7.3.4.4 Determination of Iron in the Test Solution and Blank
iron (III) oxide into a 250-mL beaker. Add 50 mL of HCl
Test—Measure the absorbance of the test solution (7.3.2) and
(7.2.5) and cover with a watch glass. Heat until the solution
1 the blank test (7.3.3) using the same conditions as used for the
boils gently for ⁄2h or until no visible particles are left.
calibration solutions (7.3.4.3). Read the concentration of the
Quantitatively transfer the contents to a 1000-mL volumetric
test solution and the blank test by reference to the calibration
flask and dilute to the mark with water. Alternatively, an
curve (7.3.4.3).
appropriate commercially available iron standard with an
7.4 Calculation:
equivalent acid concentration may be used.
7.4.1 Calculate the percentage of pyritic sulfur as follows:
7.2.8 Lanthanum Solution—Dissolve 175 g of lanthanum
chloride (LaCl ) or 265 g of hydrated lanthanum chloride
Pyritic sulfur, % 5 @F 3 A 3 V 3 C 3 P 3 ~T 2 B!#/W (2)
(LaCl ·7H O) in water and dilute to 1 L. Alternatively, slurry
3 2
where:
115 g of lanthanum oxide (La O ) in 200 mL of water. Slowly
2 3
F 5 1.148, dimen
...
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