ASTM D4371/D4371M-06(2019)e1

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D4371/D4371M − 06 (Reapproved 2019)
Standard Test Method for
Determining the Washability Characteristics of Coal
This standard is issued under the fixed designation D4371/D4371M; 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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—The designation was editorially updated to dual and other editorial changes were made throughout in December
2019.
INTRODUCTION
TheAmerican Society for Testing and Materials has recognized the need for a standard procedure
to conduct washability analyses that will serve as an aid to technical communication among
individuals and organizations that supply, purchase, and utilize coal. This test method standardizes
procedures utilized for performing washability analyses, the data from which can be used for
interpretingpreparationplantefficiency,fordeterminingpreparationplantdesign,andfordetermining
the potential recovery and quality of coal reserves.
1. Scope of the user of this standard to establish appropriate safety,
health, and environmental practices and determine the appli-
1.1 This test method describes procedures for determining
cability of regulatory limitations prior to use. For specific
the washability characteristics of coarse-coal fractions and
hazard statements, see Section 8 and Appendix X1.
fine-coal fractions. Each sample being tested can have more
1.5 This international standard was developed in accor-
than one coarse-coal size fraction and more than one fine-coal
dance with internationally recognized principles on standard-
size fraction (see Annex A1). Each such size fraction has an
ization established in the Decision on Principles for the
upper size limit and a lower size limit, neither of which
Development of International Standards, Guides and Recom-
overlaps with the next larger nor smaller size fraction. (See
mendations issued by the World Trade Organization Technical
Test Method D4749.)
Barriers to Trade (TBT) Committee.
1.2 While,ingeneral,thistestmethodhasusefulapplication
in determining the washability characteristics of low-rank
2. Referenced Documents
coals, in the strictest sense, it is not necessarily the most
2.1 ASTM Standards:
technically correct test method to determine washability char-
D2013Practice for Preparing Coal Samples for Analysis
acteristicsoflow-rankcoalsbecauseofproblemsrelativetothe
D2234/D2234MPractice for Collection of a Gross Sample
loss of moisture through drying during sample preparation and
of Coal
analysis.Methodsthataredirectlyapplicabletolow-rankcoals
D4749Test Method for Performing the Sieve Analysis of
are to be developed.
Coal and Designating Coal Size
1.3 The values stated in either SI units or inch-pound units
D6883Practice for Manual Sampling of Stationary Coal
are to be regarded separately as standard. The values stated in
from Railroad Cars, Barges, Trucks, or Stockpiles
each system are not necessarily exact equivalents; therefore, to
E11Specification forWovenWireTest Sieve Cloth andTest
ensure conformance with the standard, each system shall be
Sieves
used independently of the other, and values from the two
E100Specification for ASTM Hydrometers
systems shall not be combined.
E126Test Method for Inspection, Calibration, and Verifica-
1.4 This standard does not purport to address the safety
tion of ASTM Hydrometers
concerns, if any, associated with its use. It is the responsibility
E323Specification for Perforated-Plate Sieves for Testing
Purposes
This test method is under the jurisdiction of ASTM Committee D05 on Coal
and Coke and is the direct responsibility of Subcommittee D05.07 on Physical
Characteristics of Coal. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2019. Published December 2019. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1984. Last previous edition approved in 2012 as D4371–06(2012). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D4371_D4371M-06R19E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D4371/D4371M − 06 (2019)
3. Terminology specific gravity fraction that sinks in a certain solution of
specific gravity liquids.
3.1 Definitions:
3.1.1 coal washability—the determination of the theoretical
4. Summary of Test Method
limits for the removal of mineral impurities from coal by
4.1 Procedure A—Describes a washability procedure for
beneficiation processes that rely on specific gravity separa-
tions. coalfractionscomposedofparticlesofcoalthatarelargerthan
a specified, predetermined size, generally between 2.36 mm
3.2 Definitions of Terms Specific to This Standard:
[No. 8 USAStandard Sieve Series] and 9.5 mm [ ⁄8 in.] round
3.2.1 washability analysis of coal—the analysis of the
in diameter. These coal fractions will be referred to as
specific gravity distribution of chemical and physical charac-
coarse-coal fractions.
teristics of coal.
4.1.1 Each coarse-coal size fraction is independently sepa-
3.2.1.1 Discussion—In this test method, the specific gravity
rated into two distinct specific gravity fractions by placing the
fractions are obtained by subjecting the material being studied
sample into a large tank of sufficient capacity, for example,
to a series of solutions, each with a discrete specific gravity,
40Lto80L[10galto20gal],containingascreenbasketinsert
thatcovertherangeofspecificgravitiesinquestion.Inthecase
and a solution of organic liquids adjusted to the required
ofthewashabilityanalysisofcoal,thesesolutionsareobtained
specific gravity. The suspension is stirred gently to assure that
bythemixingofvariousorganicliquidsthatarerelativelyinert
allparticlesareallowedtoeitherfloatorsink.Thematerialthat
toward the majority of coal types. The distribution, as deter-
floats on the solution is removed first, followed by the portion
mined by the analysis, is affected by the physical condition of
of sample that sinks.
the sample subjected to the washability analysis, for example,
4.2 Procedure B—Describes a washability procedure for
the moisture content and the size content of the material.
coal fractions composed of particles of coal that are smaller
3.2.2 coarse coal—that portion of a coal sample being
thanthespecified,predeterminedsizechosenin4.1.Thesecoal
subjected to a washability study that is larger than a specific
fractions will be referred to as fine-coal fractions.
predeterminedparticlesize,generallybetween2.36mm[No.8
4.2.1 Each fine-coal size fraction is separated into two
USA Standard Sieve Series] and 9.5 mm [ ⁄8 in.] round in
distinct specific gravity fractions by placing a portion of the
diameter.
fine-coalsampleintoafloat/sinkflaskofsufficientcapacity,for
3.2.2.1 Discussion—This same particle size breakpoint
example, 2L to 4 L [0.5gal to 1 gal], containing a solution of
should then be used in subsequent washability studies of the
organic liquids adjusted to the required specific gravity (Note
same material sampled from the same location for the same
1,Note2,Note3,andNote4).Extremecaremustbeexercised
application.Thisbreakpointisdeterminedbytheanalystorthe
to avoid overloading the float/sink flask. This suspension is
person designing the test procedure as the point that best suits
thenstirredtobecertainthateachindividualparticleisallowed
theapplication.Thiscoarse-coalfractionmaybefurthersieved
to float or sink. The material that floats is removed first by
(generally by dry-sieving) to produce additional size fractions,
carefully inserting a stopper into the neck of the flask and
each of which is processed through the desired specific gravity
pouring the organic solution and float material from the upper
solutions.
portion of the float/sink flask through a filtering medium that
traps the float material. The sink material is then removed and
3.2.3 fine coal—that portion of a coal sample being sub-
captured in a similar manner.
jected to a washability study that is smaller than the predeter-
mined particle size generally between 2.36 mm [No. 8 USA
NOTE 1—A limited number of laboratories are currently using separa-
Standard Sieve Series] and 9.5 mm [ ⁄8 in.] round in diameter,
toryfunnelsfortheseparationoffinecoalparticleshavingadiameterless
which is specified in 3.2.2. than one third the diameter of the stopcock port.
NOTE 2—Some laboratories use centrifugal methods of separating
3.2.3.1 Discussion—This same particle size breakpoint
fine-coal density fractions. Centrifugal methods are not a part of this test
should then be used in subsequent washability studies of the
method.Apossible source of information is the Bureau of Mines’ Report
same material sampled from the same location for the same
of Investigations 5741 (1), or the Department of Energy, Pittsburgh
application.Thisbreakpointisdeterminedbytheanalystorthe
Energy Technology Center, Coal Preparation Branch, P.O. Box 10940,
Pittsburgh, PA 15236.
person designing the test procedure as the point which best
NOTE3—Preparationandadjustmentoftheorganicsolutionsshouldbe
suits the application. This fine-coal fraction may be further
done in an unrestricted container to allow proper mixing of the reagents
sieved (generally by wet-sieving) to produce additional size
prior to their introduction into the float/sink flasks.
fractions, each of which is processed through the desired
NOTE 4—It is a general guide that the depth of the particles floating
specific gravity solutions.
should not exceed three to five times the mean diameter of the particles in
the sample. It is suggested to use 200 g, or less.
3.2.4 float/sink—a reference to the physical action that
4.3 Preparation of Test Sample, Sieving:
particles undergo when immersed in a liquid of a predeter-
mined specific gravity. 4.3.1 The bulk sample should be spread on an impervious
base, preferably under shelter.The sample should be dried and
3.2.4.1 Discussion—Aseriesoffloat/sinktestsisconsidered
as being synonymous with a washability analysis. A float
fraction or float material is the material or the specific gravity
fraction that floats in a certain solution of specific gravity
The boldface numbers in parentheses refer to the list of references appended to
liquids. A sink fraction or sink material is the material or the this standard.
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D4371/D4371M − 06 (2019)
TABLE 1 Typical Coal Mass For Four To Six Specific Gravity
sievedinaccordancewithTestMethodD4749,usingasuitable
Fractions
range of apertures. (Apertures must conform to Specification
Mass of Material
E11 or E323.)
Needed for Washability
4.3.2 Where it is possible that some fines agglomerate or
Size Fraction Analysis of that Size
adhere to larger particles, it is important that wetsieving be
Fraction,
kg [lb]
used to ensure that fine material reports to the correct particle
200 mm × 100 mm [8 in. × 4 in. round] 2720 [6000]
size fraction. However, under normal circumstances where
100 mm × 50 mm [4 in. × 2 in. round] 910 [2000]
air-dryinghasoccurred,itshouldnotbenecessarytowet-sieve
50 mm × 25 mm [2 in. × 1 in. round] 225 [500]
the material larger than 3.15 mm [ ⁄8 in.]. 25 mm × 12.5 mm [1 in. × ⁄2 in. round] 90 [200]
1 1
12.5 mm × 6.3 mm [ ⁄2 in. × ⁄4 in. round] 25 [50]
4.3.3 As a practical guide, the presence of minus 75µm
6.3mm×2.36mm[ ⁄4 in. × No. 8 USA Standard] 9 [20]
[No. 200 USA Standard] material should be minimized,
2.36 mm × 1.40 mm [No. 8 × No. 14 USA Standard] 5 [10]
because Brownian movement or molecular interference can be 1.40 mm × 600 µm [No. 14 × No. 30 USA Standard] 2 [5]
600 µm × 300 µm [No. 30 × No. 50 USA Standard] 1 [2]
detrimental to proper and efficient separations. Minus 75µm
300 µm × 150 µm [No. 50 × No. 100 USA Standard] 0.5 [1]
[No. 200 USAStandard] material can then be processed using
150 µm × 75 µm [No. 100 × No. 200 USA Standard] 0.5 [1]
separate test procedures. (See, for example, the reference in
Note 2.)
4.3.4 When required, material which is larger than the
desired topsize is broken by hand or machine-crushed accord-
principal criteria being that it should be unaffected by the
ing to the topsize required, or, if applicable, by simulating the
solutions involved (that is, the organic liquids do not corrode,
relevant part of the crushing circuit.
etch, or otherwise react with the materials from which the
apparatus is constructed) and that it should be convenient for
5. Significance and Use
use (see X1.3). Types of apparatus that have been found to be
5.1 Although the determination of the washability charac-
suitable are discussed in the following subsections and are
teristics of coal is not an exact science, this washability test
illustrated in Fig. 1, Fig. 2, and Fig. 3.
method can be used to investigate the cleaning characteristics
6.2 Suitable Float/Sink Container for Coarse-Coal
ofcoarse-andfine-coalfractions.However,especiallywiththe
Fractions—The float/sink apparatus may consist of a wire
fine-coal fractions, this test method may not be applicable for
mesh insert and a holding tank (Fig. 1 and Fig. 2). The wire
low-rank coals for reasons explained in 1.2.
mesh insert should consist entirely of wire mesh, have solid
5.2 The usefulness of this test procedure and the usefulness
sides with a wire mesh bottom, or have a solid bottom with
of the results derived from washability testing are directly
wiremeshsides.Thewiremeshusedmustbesmallerthanone
related to the care exercised in developing and following the
half the size of the finest coal in the fraction. The insert fits
sampling regime while taking into consideration the desired
inside the holding tank. The insert may have handles attached
degree of precision. For more exacting work, it will be
or may utilize an overhead lifting device to facilitate removal
necessarytoknowthegeneralwashabilitycharacteristicsofthe
from the tank. A typical laboratory holding tank has approxi-
material in question. This can be done only through pilot
mately40Lto80L[10galto20gal]capacity.Tankandinsert
testing as described in 9.6 and Annex A3.
must be designed so as to be compatible.
5.3 This test method, in conjunction with the advice of
NOTE 5—It is possible that the geometry of the tank may have some
experts and with knowledge of the particle size analysis (see
effect on the ease with which the materials are removed from the tank.
TestMethodD4749),isusedfortheengineeringdesignofc
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