ASTM D4371/D4371M-06(2019)e1

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.
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 either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 8 and Appendix X1.  
1.5 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.

General Information

• Status: Published
• Publication Date: 31-Oct-2019
• ICS: 75.160.10 - Solid fuels
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.07 - Physical Characteristics of Coal

Relations

• Replaces: ASTM D4371-06(2012) - Standard Test Method for Determining the Washability Characteristics of Coal
• Effective Date: 01-Nov-2019
• Refers: ASTM D2234/D2234M-19 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Dec-2019
• Refers: ASTM E126-19 - Standard Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
• Effective Date: 01-May-2019
• Refers: ASTM E100-19 - Standard Specification for ASTM Hydrometers
• Effective Date: 01-May-2019
• Refers: ASTM D6883-17 - Standard Practice for Manual Sampling of Stationary Coal from Railroad Cars, Barges, Trucks, or Stockpiles
• Effective Date: 15-Oct-2017
• Refers: ASTM D2234/D2234M-17 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 15-Oct-2017
• Refers: ASTM D2234/D2234M-16 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Mar-2016
• Refers: ASTM E100-15a - Standard Specification for ASTM Hydrometers
• Effective Date: 01-Dec-2015
• Refers: ASTM E100-15 - Standard Specification for ASTM Hydrometers
• Effective Date: 01-Aug-2015
• Refers: ASTM E100-14 - Standard Specification for ASTM Hydrometers
• Effective Date: 01-May-2014
• Refers: ASTM E126-13a - Standard Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
• Effective Date: 01-Nov-2013
• Refers: ASTM E11-13 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-Oct-2013
• Refers: ASTM E126-13 - Standard Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
• Effective Date: 01-May-2013
• Refers: ASTM E126-12 - Standard Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
• Effective Date: 15-Nov-2012
• Refers: ASTM E323-11 - Standard Specification for Perforated-Plate Sieves for Testing Purposes
• Effective Date: 15-Nov-2011

Overview

ASTM D4371/D4371M-06(2019)e1 is a standard test method developed by ASTM International for determining the washability characteristics of coal. Understanding coal washability is crucial for industries involved in coal mining, coal processing, and coal utilization, as it helps to assess the efficiency of separating coal from impurities through physical beneficiation processes based on specific gravity separations. This standard outlines procedures for both coarse-coal and fine-coal size fractions, offering a consistent framework to evaluate how efficiently coal can be cleaned and upgraded for various industrial applications.

Key Topics

• Coal Washability: The test method determines the theoretical limits of removing mineral impurities from coal by evaluating specific gravity fractions. Both coarse and fine size fractions are assessed without overlap between size ranges.
• Sampling and Precision: The accuracy of results heavily depends on careful sampling and adherence to standardized procedures. For detailed engineering and process control, pilot testing and geostatistical consideration may be required.
• Procedure: The standard describes laboratory procedures for float/sink analysis, using organic liquids of known specific gravity to separate fractions of coal according to their density.
• Limitations: The method may have constraints when applied to low-rank coals due to moisture loss during preparation and analysis. Special methods may be necessary for these coal types.
• Safety and Environmental Considerations: Users must implement appropriate safety, health, and environmental practices, and comply with relevant local regulations when performing the test.

Applications

ASTM D4371/D4371M has several practical applications across the coal industry:

• Coal Preparation Plant Design: The washability data provided by this method are essential for the engineering design of facilities dedicated to coal cleaning and preparation, ensuring optimal separation of coal from mineral matter.
• Process Control and Plant Efficiency: Regular washability analysis aids in monitoring and controlling the efficiency of operating coal preparation plants, helping to maximize product quality and recovery.
• Coal Core Studies and Reserve Evaluation: In exploration and reserve assessment, this method helps determine the potential recovery and quality of coal, guiding resource valuation and mine planning.
• Technical Communication: By standardizing procedures and terminology, the method promotes clear communication among suppliers, buyers, and users of coal regarding its cleaning characteristics and potential market value.

Related Standards

To ensure thorough analysis and consistent results, ASTM D4371/D4371M references several related ASTM coal and materials testing standards, including:

• ASTM D2013: Practice for Preparing Coal Samples for Analysis
• ASTM D2234/D2234M: Practice for Collection of a Gross Sample of Coal
• ASTM D4749: Test Method for Sieve Analysis of Coal and Designating Coal Size
• ASTM D6883: Practice for Manual Sampling of Stationary Coal
• ASTM E11: Specification for Woven Wire Test Sieve Cloth and Test Sieves
• ASTM E100: Specification for ASTM Hydrometers
• ASTM E126: Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
• ASTM E323: Specification for Perforated-Plate Sieves for Testing Purposes

Practical Value

By adhering to ASTM D4371/D4371M, stakeholders in the coal industry can:

• Achieve reliable, repeatable washability analysis
• Identify optimal coal cleaning processes
• Improve the economic value of coal products
• Meet industry, environmental, and market requirements
• Facilitate international trade through standardized reporting and compliance

Keywords: ASTM D4371, coal washability, coal preparation, float/sink test, coal core analysis, washability test method, coal cleaning, coal beneficiation, coal standard, ASTM standards.

Standards Content (Sample)

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.
´1
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 [e-mail]. 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
´1
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.
´1
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),isusedfortheengineeringdesignofcoal
Square tanks have the following disadvantages: (a) it is difficult to get the
preparation facilities.
wire mesh strainer into the corners to remove all of the float material, and
(b) material, especially the sink fraction, may be trapped in the corners
5.4 This test method is also used to assist in process control
while the material is being removed from the tank.
and to determine the efficiency of operating preparation plants.
6.3 Suitable Float/Sink Flask for Fine-Coal Fractions—The
5.5 This test method is used in core studies to determine the
float/sink flasks, that typically have a capacity of 2L to 4 L
qualitywashabilitycharacteristicsofcoalreserves;however,in
[0.5gal to 1 gal], should be constructed with ground glass
these instances the typical mass of raw coal from Table 1 may
connecting joints (see Fig. 3).
be neither applicable nor practical. For this reason, core
6.4 Additional Apparatus:
diameter should be as large as possible and subdivision of the
6.4.1 Balance, suggested 2000 g capacity, sensitive to
core section by any means or for any purpose prior to
60.1g, for weighing small samples or fractions.
washability testing should be avoided. Care must be exercised
6.4.2 Balance, suggested 0kg to 110kg [0lb to 250lb]
in the design of the coring programs, including the consider-
capacity, sensitive to 645 g [0.10 lb] for weighing large
ation of appropriate geostatistics, in order that the potential
samples or fractions.
recovery and quality of the coal reserves, as defined by the
6.4.3 Wire Mesh Strainers, with mesh size one half of the
washability analysis of the cores, have any practical signifi-
size of the smallest particle.
cance.
6.4.4 VacuumorPressureFilter,orFilterFunnelforgravity
6. Apparatus
filtration.
6.1 The suggested apparatus to be used should be as simple 6.4.5 Drying Oven, forced air, heatable to 40°C with
as possible and be commensurate with the test objective—the adequate and proper ventilation.
´1
D4371/D4371M − 06 (2019)
FIG. 1 Suitable Rectangular Float and Sink Apparatus for Separation of Coarse-Coal Fractions
6.4.6 Hydrometers, series within the working range desired, medium and it is recommended that aqueous suspensions not
compatible with Specification E100 and Test Method E126. be used as the medium for washability analysis.
6.4.7 Hydrometer or Graduated Cylinder of sufficient size.
7.1.1 The most suitable range of relative densities is depen-
6.4.8 Dispenser, plastic, squeeze, unaffected by the organic
dentuponthespecificpurposeofthetestandthecharacteristics
liquids being used.
of the specific coal, but would typically include 1.3, 1.4, 1.5,
1.6,1.7,1.8,and2.0specificgravitieswithadditionalgravities
7. Reagents and Materials
if desired.
7.1 General Consideration—Media that have been used for
7.2 Organic Liquids—The following organic liquids, shown
the separation include solutions of organic liquids, aqueous
with their relative densities, are generally used for preparation
solutions of inorganic salts, and solids in aqueous suspensions.
ofwashabilitymedia:petroleumspirit(0.7),whitespirit(0.77),
The choice of medium is governed to some extent by the bulk
naphtha (0.79), toluene (0.86), perchloroethylene (1.6), meth-
and particle size of the coal being tested, its rank, relative
ylene bromide (2.49), bromoform (2.9), and tetrabromoethane
density, and the purpose for which the separation is being
performed. Solutions of organic liquids are the preferred (2.96).
´1
D4371/D4371M − 06 (2019)
FIG. 2 Suitable Cylindrical Float and Sink Apparatus for Separation of Coarse-Coal Fractions
7.2.1 Information on preferability for organic liquids, their 9. Sampling and Test Specimens
volatility, specific gravity, specific gravity measurements, and
9.1 Obtaining analytical results that truly represent the
subsequent treatment for removal is included in Annex A2.
material being sampled requires planning and diligence in
NOTE 6—Warning: Some of these organic liquids may be hazardous. takingthesampleanditsstorage,handling,andpreparation (2,
See Appendix X1.
3, 4, 5, 6, 7, 8, 9).Thewidevarietiesofcoalhandlingfacilities,
the wide differences in physical constraints on the various
8. Hazards
sampling locations, and the various uses of coal washability
data preclude the publication of detailed recommendations for
8.1 The most commonly used organic solutions produce
the sampling of coal for every situation. Sampling and sample
vapors and must be used only in a well-ventilated or hooded
area. In addition to adequate ventilation, it is also prudent to preparation, therefore, should be done in accordance with Test
use appropriate safety measures. (See Appendix X1.)
´1
D4371/D4371M − 06 (2019)
Method D4749) to determine the actual mass that can be
expected in each size fraction.
9.5 When taking a bulk sample, it is better to sample
excessively than to have insufficient material. For instance, the
masses given in Table 1 may be too small for certain
requirements, such as performance testing a preparation plant
or where extensive analytical work is required. Because some
coals give low yield in middle specific gravity fractions, there
maybeinsufficientmaterialforanalyticalrequirementsandthe
mass of the bulk sample may have to be increased to meet the
general guideline of having not less than 20 g nor less than 10
particles in each specific gravity fraction. It may be necessary
to increase the mass of the original bulk sample to assure that
this guideline is met or, alternatively, specific gravity fractions
not meeting this requirement should be added to the appropri-
ate adjacent fraction before weighing and analyzing.
NOTE7—Itmaybepossible,withthesmallersizefractions,tocomplete
the washability analysis with less than 20g recovery per specific gravity
fraction,especiallyifonlylimitedanalysesaretobeperformeduponthese
fractions.However,duetopotentialrecovery,weighing,andinterpretation
NOTE 1—Handle and rubber stopper are put in place as shown only
errors, these data should be cautiously reported and used. In such cases,
when the float/sink flasks are to be disassembled for recovering the float
the actual mass of material recovered from such specific gravity fractions
and sink fractions.
is reported on each analytical report.
FIG. 3 Suitable Float and Sink Apparatus for Separation of Fine-
9.6 Pilot testing is frequently performed on a representative
Coal Fractions
sample in order to estimate the gross washability characteris-
tics of the bulk materials. The knowledge gained allows for
MethodsD2234/D2234M,PracticeD6883andMethodD2013.
betterplanningofsamplingandwashabilityanalysisonalarge
Toassurethatasufficientamountofmaterialiscollected,refer
scale. See Annex A3 for details.
to Table 1.
9.2 The quantity of sample and the degree of accuracy
10. Preparation of Apparatus
desired in a float and sink test varies according to the purpose
NOTE 8—Warning: The organic solutions used in this procedure may
for which the test is being performed, the four main categories
be hazardous. See Section 8 and Appendix X1 for precautionary state-
being as follows:
ments.
9.2.1 Investigation of the characteristics of raw coal,
10.1 Coarse-Coal Fractions:
9.2.2 Comprehensive plant and equipment performance
10.1.1 Withthewiremeshinsertsinplace,preparethelarge
tests,
float/sink tanks by filling the tanks three quarters full with the
9.2.3 Determination of preparation plant design, and
first specific gravity solution that is required for the test.
9.2.4 Plant control testing.
10.1.2 Establish the desired specific gravity of the solution
9.3 The amount of material required, the care to be exer-
in accordance with 11.2.
cised in performing the washability analysis, and the degree of
10.2 Fine-Coal Fractions:
precision and bias obtained will vary with the purpose for
which the analysis is conducted. For this reason, it is para-
10.2.1 Prepare the float/sink flasks of 2L to 4L [0.5gal to
mount that rigid control of the appropriate parameters be 1gal] capacity by filling to within 50 mm [2 in.] of the top of
exercised throughout the washability procedure.
the first specific gravity solution that is required for the test
(Note 3).
9.4 As a general guide for a washability analysis of four to
10.2.2 Establish the desired specific gravity of the solution
sixspecificgravities,themassofthegrosssamplesubjectedto
in accordance with 11.2.
washabilityanalysistypicallyislargeenoughtoyieldthelisted
quantity in each size fraction upon sieving as listed in Table 1.
11. Calibration and Standardization
9.4.1 This requirement is usually met by using the gross
sample mass resulting from the required mass of the topsize
11.1 At regular intervals, as dictated by good laboratory
fraction; for example, for 100 mm×600 µm [4 in.×No. 30
practice, calibrate all hydrometers in accordance wit
...