ASTM D4371-06(2012)
(Test Method)Standard Test Method for Determining the Washability Characteristics of Coal
Standard Test Method for Determining the Washability Characteristics of Coal
SIGNIFICANCE AND USE
5.1 Although the determination of the washability characteristics of coal is not an exact science, this washability test method can be used to investigate the cleaning characteristics of coarse- and fine-coal fractions. However, especially with the fine-coal fractions, this test method may not be applicable for low-rank coals for reasons explained in 1.2.
5.2 The usefulness of this test procedure and the usefulness of the results derived from washability testing are directly related to the care exercised in developing and following the sampling regime while taking into consideration the desired degree of precision. For more exacting work, it will be necessary to know the general washability characteristics of the material in question. This can be done only through pilot testing as described in 9.6 and Annex A3.
5.3 This test method, in conjunction with the advice of experts and with knowledge of the particle size analysis (see Test Method D4749), is used for the engineering design of coal preparation facilities.
5.4 This test method is also used to assist in process control and to determine the efficiency of operating preparation plants.
5.5 This test method is used in core studies to determine the quality washability characteristics of coal reserves; however, in these instances the typical mass of raw coal from Table 1 may be neither applicable nor practical. For this reason, core diameter should be as large as possible and subdivision of the core section by any means or for any purpose prior to washability testing should be avoided. Care must be exercised in the design of the coring programs, including the consideration of appropriate geostatistics, in order that the potential recovery and quality of the coal reserves, as defined by the washability analysis of the cores, have any practical significance.TABLE 1 Typical Coal Mass For Four To Six Specific Gravity Fractions
Size Fraction
Mass of Material Needed for Washability Analysis of that Siz...
SCOPE
1.1 This test method describes procedures for determining the washability characteristics of coarse-coal fractions and fine-coal fractions. Each sample being tested can have more than one coarse-coal size fraction and more than one fine-coal size fraction (see Annex A1). Each such size fraction has an upper size limit and a lower size limit, neither of which overlaps with the next larger nor smaller size fraction. (See Test Method D4749.)
1.2 While, in general, this test method has useful application in determining the washability characteristics of low-rank coals, in the strictest sense, it is not necessarily the most technically correct test method to determine washability characteristics of low-rank coals because of problems relative to the loss of moisture through drying during sample preparation and analysis. Methods that are directly applicable to low-rank coals are to be developed.
1.3 The values stated in SI units are to be regarded as the standard. The values shown in parentheses are for information only.
1.4 This standard does not purport to address 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. For specific hazard statements, see Section 8 and Appendix X1.
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Designation: D4371 − 06 (Reapproved 2012)
Standard Test Method for
Determining the Washability Characteristics of Coal
This standard is issued under the fixed designation D4371; 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.
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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method describes procedures for determining
D2013Practice for Preparing Coal Samples for Analysis
the washability characteristics of coarse-coal fractions and
D2234/D2234MPractice for Collection of a Gross Sample
fine-coal fractions. Each sample being tested can have more
of Coal
than one coarse-coal size fraction and more than one fine-coal
D4749Test Method for Performing the Sieve Analysis of
size fraction (see Annex A1). Each such size fraction has an
Coal and Designating Coal Size
upper size limit and a lower size limit, neither of which
D6883Practice for Manual Sampling of Stationary Coal
overlaps with the next larger nor smaller size fraction. (See
from Railroad Cars, Barges, Trucks, or Stockpiles
Test Method D4749.)
E11Specification forWovenWireTest Sieve Cloth andTest
1.2 While,ingeneral,thistestmethodhasusefulapplication
Sieves
in determining the washability characteristics of low-rank
E100Specification for ASTM Hydrometers
coals, in the strictest sense, it is not necessarily the most
E126Test Method for Inspection, Calibration, and Verifica-
technically correct test method to determine washability char-
tion of ASTM Hydrometers
acteristicsoflow-rankcoalsbecauseofproblemsrelativetothe
E323Specification for Perforated-Plate Sieves for Testing
loss of moisture through drying during sample preparation and
Purposes
analysis.Methodsthataredirectlyapplicabletolow-rankcoals
are to be developed.
3. Terminology
3.1 Definitions:
1.3 The values stated in SI units are to be regarded as the
standard. The values shown in parentheses are for information 3.1.1 coal washability—the determination of the theoretical
limits for the removal of mineral impurities from coal by
only.
beneficiation processes that rely on specific gravity separa-
1.4 This standard does not purport to address the safety
tions.
concerns, if any, associated with its use. It is the responsibility
3.2 Definitions of Terms Specific to This Standard:
of the user of this standard to establish appropriate safety and
3.2.1 washability analysis of coal—the analysis of the
health practices and determine the applicability of regulatory
specific gravity distribution of chemical and physical charac-
limitations prior to use. For specific hazard statements, see
teristics of coal.
Section 8 and Appendix X1.
3.2.1.1 Discussion—In this test method, the specific gravity
fractions are obtained by subjecting the material being studied
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 Sept. 1, 2012. Published November 2012. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
published as approved in 1984. Last previous edition approved in 2006 as Standards volume information, refer to the standard’s Document Summary page on
D4371–2006. DOI: 10.1520/D4371-06R12. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4371 − 06 (2012)
to a series of solutions, each with a discrete specific gravity, solution of organic liquids adjusted to the required specific
thatcovertherangeofspecificgravitiesinquestion.Inthecase gravity. The suspension is stirred gently to assure that all
ofthewashabilityanalysisofcoal,thesesolutionsareobtained particles are allowed to either float or sink. The material that
bythemixingofvariousorganicliquidsthatarerelativelyinert floats on the solution is removed first, followed by the portion
toward the majority of coal types. The distribution, as deter- of sample that sinks.
mined by the analysis, is affected by the physical condition of
4.2 Procedure B—Describes a washability procedure for
the sample subjected to the washability analysis, for example,
coal fractions composed of particles of coal that are smaller
the moisture content and the size content of the material.
thanthespecified,predeterminedsizechosenin4.1.Thesecoal
3.2.2 coarse coal—that portion of a coal sample being
fractions will be referred to as fine-coal fractions.
subjected to a washability study that is larger than a specific
4.2.1 Each fine-coal size fraction is separated into two
predeterminedparticlesize,generallybetween2.36mm(No.8
distinct specific gravity fractions by placing a portion of the
USA Standard Sieve Series) and 9.5 mm ( ⁄8 in.) round in
fine-coalsampleintoafloat/sinkflaskofsufficientcapacity,for
diameter.
example, 2 to 4 L (0.5 to 1 gal), containing a solution of
3.2.2.1 Discussion—This same particle size breakpoint
organic liquids adjusted to the required specific gravity (Note
should then be used in subsequent washability studies of the
1,Note2,Note3,andNote4).Extremecaremustbeexercised
same material sampled from the same location for the same
to avoid overloading the float/sink flask. This suspension is
application.Thisbreakpointisdeterminedbytheanalystorthe
thenstirredtobecertainthateachindividualparticleisallowed
person designing the test procedure as the point that best suits
to float or sink. The material that floats is removed first by
theapplication.Thiscoarse-coalfractionmaybefurthersieved
carefully inserting a stopper into the neck of the flask and
(generally by dry-sieving) to produce additional size fractions,
pouring the organic solution and float material from the upper
each of which is processed through the desired specific gravity
portion of the float/sink flask through a filtering medium that
solutions.
traps the float material. The sink material is then removed and
captured in a similar manner.
3.2.3 fine coal—that portion of a coal sample being sub-
jected to a washability study that is smaller than the predeter-
NOTE 1—A limited number of laboratories are currently using separa-
mined particle size generally between 2.36 mm (No. 8 USA
toryfunnelsfortheseparationoffinecoalparticleshavingadiameterless
than one third the diameter of the stopcock port.
Standard Sieve Series) and 9.5 mm ( ⁄8 in.) round in diameter,
NOTE 2—Some laboratories use centrifugal methods of separating
which is specified in 3.2.2.
fine-coal density fractions. Centrifugal methods are not a part of this test
3.2.3.1 Discussion—This same particle size breakpoint
method.Apossible source of information is the Bureau of Mines’ Report
should then be used in subsequent washability studies of the
of Investigations 5741 (1), or the Department of Energy, Pittsburgh
same material sampled from the same location for the same
Energy Technology Center, Coal Preparation Branch, P.O. Box 10940,
Pittsburgh, PA 15236.
application.Thisbreakpointisdeterminedbytheanalystorthe
NOTE3—Preparationandadjustmentoftheorganicsolutionsshouldbe
person designing the test procedure as the point which best
done in an unrestricted container to allow proper mixing of the reagents
suits the application. This fine-coal fraction may be further
prior to their introduction into the float/sink flasks.
sieved (generally by wet-sieving) to produce additional size
NOTE 4—It is a general guide that the depth of the particles floating
fractions, each of which is processed through the desired 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.
specific gravity solutions.
4.3 Preparation of Test Sample, Sieving:
3.2.4 float/sink—a reference to the physical action that
4.3.1 The bulk sample should be spread on an impervious
particles undergo when immersed in a liquid of a predeter-
base, preferably under shelter.The sample should be dried and
mined specific gravity.
sievedinaccordancewithTestMethodD4749,usingasuitable
3.2.4.1 Discussion—Aseriesoffloat/sinktestsisconsidered
range of apertures. (Apertures must conform to Specification
as being synonymous with a washability analysis. A float
E11 or E323.)
fraction or float material is the material or the specific gravity
4.3.2 Where it is possible that some fines agglomerate or
fraction that floats in a certain solution of specific gravity
adhere to larger particles, it is important that wetsieving be
liquids. A sink fraction or sink material is the material or the
used to ensure that fine material reports to the correct particle
specific gravity fraction that sinks in a certain solution of
size fraction. However, under normal circumstances where
specific gravity liquids.
air-dryinghasoccurred,itshouldnotbenecessarytowet-sieve
4. Summary of Test Method
the material larger than 3.15 mm ( ⁄8 in.).
4.3.3 As a practical guide, the presence of minus 75-µm
4.1 Procedure A—Describes a washability procedure for
(No. 200 USA Standard) material should be minimized,
coalfractionscomposedofparticlesofcoalthatarelargerthan
because Brownian movement or molecular interference can be
a specified, predetermined size, generally between 2.36 mm
3 detrimental to proper and efficient separations. Minus 75-µm
(No. 8 USAStandard Sieve Series) and 9.5 mm ( ⁄8 in.) round
(No. 200 USAStandard) material can then be processed using
in diameter. These coal fractions will be referred to as
separate test procedures. (See, for example, the reference in
coarse-coal fractions.
Note 2.)
4.1.1 Each coarse-coal size fraction is independently sepa-
rated into two distinct specific gravity fractions by placing the
sample into a large tank of sufficient capacity, for example, 40
The boldface numbers in parentheses refer to the list of references appended to
to 80 L (10 to 20 gal), containing a screen basket insert and a this standard.
D4371 − 06 (2012)
4.3.4 When required, material which is larger than the 6. Apparatus
desired topsize is broken by hand or machine-crushed accord-
6.1 The suggested apparatus to be used should be as simple
ing to the topsize required, or, if applicable, by simulating the
as possible and be commensurate with the test objective—the
relevant part of the crushing circuit.
principal criteria being that it should be unaffected by the
solutions involved (that is, the organic liquids do not corrode,
5. Significance and Use
etch, or otherwise react with the materials from which the
apparatus is constructed) and that it should be convenient for
5.1 Although the determination of the washability charac-
use (see X1.3). Types of apparatus that have been found to be
teristics of coal is not an exact science, this washability test
suitable are discussed in the following subsections and are
method can be used to investigate the cleaning characteristics
illustrated in Fig. 1, Fig. 2, and Fig. 3.
ofcoarse-andfine-coalfractions.However,especiallywiththe
fine-coal fractions, this test method may not be applicable for
6.2 Suitable Float/Sink Container for Coarse-Coal
low-rank coals for reasons explained in 1.2.
Fractions—The float/sink apparatus may consist of a wire
mesh insert and a holding tank (Fig. 1 and Fig. 2). The wire
5.2 The usefulness of this test procedure and the usefulness
mesh insert should consist entirely of wire mesh, have solid
of the results derived from washability testing are directly
sides with a wire mesh bottom, or have a solid bottom with
related to the care exercised in developing and following the
wiremeshsides.Thewiremeshusedmustbesmallerthanone
sampling regime while taking into consideration the desired
half the size of the finest coal in the fraction. The insert fits
degree of precision. For more exacting work, it will be
inside the holding tank. The insert may have handles attached
necessarytoknowthegeneralwashabilitycharacteristicsofthe
or may utilize an overhead lifting device to facilitate removal
material in question. This can be done only through pilot
from the tank. A typical laboratory holding tank has approxi-
testing as described in 9.6 and Annex A3.
mately40to80-L(10to20-gal)capacity.Tankandinsertmust
5.3 This test method, in conjunction with the advice of
be designed so as to be compatible.
experts and with knowledge of the particle size analysis (see
NOTE 5—It is possible that the geometry of the tank may have some
TestMethodD4749),isusedfortheengineeringdesignofcoal
effect on the ease with which the materials are removed from the tank.
preparation facilities.
Square tanks have the following disadvantages: (a) it is difficult to get the
wire mesh strainer into the corners to remove all of the float material, and
5.4 This test method is also used to assist in process control
(b) material, especially the sink fraction, may be trapped in the corners
and to determine the efficiency of operating preparation plants.
while the material is being removed from the tank.
5.5 Thistestmethodisusedincorestudiestodeterminethe 6.3 Suitable Float/Sink Flask for Fine-Coal Fractions—The
float/sink flasks, that typically have a capacity of 2 to 4 L(0.5
qualitywashabilitycharacteristicsofcoalreserves;however,in
these instances the typical mass of raw coal from Table 1 may to 1 gal), should be constructed with ground glass connecting
joints (see Fig. 3).
be neither applicable nor practical. For this reason, core
diameter should be as large as possible and subdivision of the
6.4 Additional Apparatus:
core section by any means or for any purpose prior to
6.4.1 Balance,suggested2000-gcapacity,sensitiveto 60.1
washability testing should be avoided. Care must be exercised
g, for weighing small samples or fractions.
in the design of the coring programs, including the consider-
6.4.2 Balance, suggested 0 to 110-kg (0 to 250-lb) capacity,
ation of appropriate geostatistics, in order that the potential
sensitive to 645 g (0.10 lb) for weighing large samples or
recovery and quality of the coal reserves, as
...
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