ASTM D409-02(2007)e1
(Test Method)Standard Test Method for Grindability of Coal by the Hardgrove-Machine Method
Standard Test Method for Grindability of Coal by the Hardgrove-Machine Method
SIGNIFICANCE AND USE
This test method develops a measurement of grinding or pulverizing characteristics that can be used to evaluate the yield, or energy input, or both, required in a grinding or pulverizing process.
SCOPE
1.1 This test method covers the determination of the relative grindability or ease of pulverization of coals in comparison with coals chosen as standards. A prepared and sized sample receives a definite amount of grinding energy in a miniature pulverizer, and the size consist of the pulverized product is determined by sieving. The resultant size consist is used to produce an index relative to the ease of grinding (Hardgrove Grindability Index (HGI)).
1.1.1 Some coals, such as some high-volatile bituminous, subbituminous, and lignite coals, can undergo physical change as the natural or seam moisture is released during handling and preparation. This change is often sufficient to alter the grindability characteristics that will be reported when tested in the laboratory and could produce different indices dependent on the conditions of drying and the moisture level of the 1.18-mm by 600-m (No. 16 No. 30) (see Test Method D 4749) materials used for the test. Therefore, the repeatability and reproducibility cited in this test method may not apply for these high-volatile bituminous, subbituminous, and lignite coals.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses may be approximate.
1.3 It is recognized that the term weight is considered equivalent to mass as used in this test method.
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:D409–02 (Reapproved 2007)
Standard Test Method for
Grindability of Coal by the Hardgrove-Machine Method
This standard is issued under the fixed designation D409; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Section 10.2 was editorially corrected in October 2007.
1. Scope 2. Referenced Documents
2 3
1.1 This test method covers the determination of the 2.1 ASTM Standards:
relative grindability or ease of pulverization of coals in D2013 Practice for Preparing Coal Samples for Analysis
comparison with coals chosen as standards. A prepared and D2234/D2234M PracticeforCollectionofaGrossSample
sized sample receives a definite amount of grinding energy in of Coal
a miniature pulverizer, and the size consist of the pulverized D4749 Test Method for Performing the Sieve Analysis of
product is determined by sieving. The resultant size consist is Coal and Designating Coal Size
used to produce an index relative to the ease of grinding E11 Specification for Wire Cloth and Sieves for Testing
(Hardgrove Grindability Index (HGI)). Purposes
1.1.1 Some coals, such as some high-volatile bituminous,
3. Significance and Use
subbituminous, and lignite coals, can undergo physical change
asthenaturalorseammoistureisreleasedduringhandlingand 3.1 Thistestmethoddevelopsameasurementofgrindingor
pulverizing characteristics that can be used to evaluate the
preparation. This change is often sufficient to alter the grind-
ability characteristics that will be reported when tested in the yield, or energy input, or both, required in a grinding or
pulverizing process.
laboratory and could produce different indices dependent on
theconditionsofdryingandthemoisturelevelofthe1.18-mm
4. Apparatus
by 600-µm (No. 16 3No. 30) (see Test Method D4749)
4.1 Air-Drying Oven—A device for passing slightly heated
materials used for the test. Therefore, the repeatability and
air over the sample. The oven shall be capable of maintaining
reproducibilitycitedinthistestmethodmaynotapplyforthese
a temperature of 10 to 15°C (18 to 27°F) above room
high-volatile bituminous, subbituminous, and lignite coals.
temperature with a maximum oven temperature of 40°C
1.2 The values stated in SI units are to be regarded as the
(104°F) unless ambient temperature is above 40°C, in which
standard.Thevaluesgiveninparenthesesmaybeapproximate.
case ambient temperature shall be used. In the case of easily
1.3 It is recognized that the term weight is considered
oxidized coals, the temperature shall not be over 10°C (18°F)
equivalent to mass as used in this test method.
above room temperature unless ambient temperature is above
1.4 This standard does not purport to address all of the
37°C(100°F)inwhichcaseambienttemperatureshallbeused.
safety concerns, if any, associated with its use. It is the
Air changes shall be at the rate of 1 to 4 air volumes of oven
responsibility of the user of this standard to establish appro-
capacity per minute.
priate safety and health practices and determine the applica-
4.2 Drying Pans—Drying pans of sufficient size so that the
bility of regulatory limitations prior to use.
sample may be spread to a depth of not more than 25 mm (1.0
in.) with sides not more than 38 mm (1.5 in.) high. The pans
This test method is under the jurisdiction of ASTM Committee D05 on Coal
shall be nonreactive with coal and unaffected by the method of
and Coke and is the direct responsibility of D05.07 on Physical Characteristics of
air drying selected.
Coal.
4.3 Balances—Two balances may be required: one with a
CurrenteditionapprovedOct.1,2007.PublishedJuly2002.Originallyapproved
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in 1951. Last previous edition approved in 2002 as D409– .
sensitivity of 10 mg and a minimum capacity of 800 g and one
Forinformationconcerningtheexperimentalworkonwhichthistestmethodis
with a sensitivity of 0.5 g in 1000 g and sufficient capacity to
based, see paper by Hardgrove, R. M., “Grindability of Coal,” Transactions,
American Society of Mechanical Engineers, Vol 54, F.S.P., p. 37, 1932.
D05.07.02 on Grindability is conducting ongoing investigations in regard to
quality control during preparation, distribution, and use of standard reference
materials and during preparation and testing of actual samples. Annual Book of ASTM Standards, Vol 05.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D409–02 (2007)
NOTE 4—The most frequently used plate mill can be equipped with
weigh a$1000-g sample along with the drying pan. A single
“fine” or “coarse” plates. One independent study has found evidence of
balance meeting these specifications is permitted.
differences in percent recovery resulting from use of different types of
4.3.1 Calibration Weights—These calibration weights shall
plate. Only the coarse plate should be used in preparation of both HGI
beusedtomonitortheresponseofeachbalanceovertherange
calibration standards and unknown samples.
of normal use each time HGIs are determined.
4.7 Mechanical Sieving Machine—The mechanical sieving
4.4 SampleDivider—Anenclosedriffledividerasdescribed
machine shall accept an assembly of vertically nested circular
in Method D2013 is required and shall be used.
sieves of 203 mm (8 in.) in diameter, together with cover and
4.5 Standard Sieves—A working set of circular, standard
receiver. The machine shall simulate the motions given testing
testing sieves which are 203 mm (8 in.) in diameter and
sieves during hand sieving by imparting a horizontal oscilla-
conform to Specification E11, are required in the following
tory motion of approximately 28-mm (1.1-in.) amplitude at a
sizes, together with cover and catch pan (receiver):
rate of approximately 300 oscillations or cycles per minute
Sieve Designation
(cpm). Simultaneously, the top of the oscillating assembly is
Standard Alternate
(ISO Designation) (U.S.A. Designation)
struck at a rate of approximately 150 blows per minute by a
weight of 1.9 kg (4.2 lb) moving through a vertical distance of
16.0 mm ⁄8 in.
approximately 28 mm (1.1 in.) under the influence of gravity.
4.75 mm No. 4
2.36 mm No. 8
4.8 Grindability Machine—The Hardgrove Grindability
1.18 mm No. 16
Machine such as is shown in Fig. 1 is required for this test.
600 µm No. 30
EssentialtolerancesandspecificationsareshowninFig.2.The
75 µm No. 200
grindability machine includes a stationary grinding bowl of
4.5.1 These working sieves must be periodically inspected
polished cast iron, with a circular horizontal track that holds
for wear or damage.Any excessively worn or damaged sieves
eight polished steel balls, each 25.40 6 0.13 mm (1.000 6
(sieveswithholes,tearscracks,andsoforth,seeNote1).must
0.005 in.) in diameter. The balls are driven by an upper
be replaced immediately, and the HGI calibration procedure
grinding ring which is rotated at 20 6 1 r/min by means of the
must be repeated after the damaged sieves are replaced (see
upperspindleandwhich,inturn,isdrivenbyanelectricmotor
Section 8). Since the HGI depends upon the sieve analysis and
through reduction gears and, in newer models, belts. Weights
since the 75-µm (No. 200) sieve is fragile, it is recommended
are added to the driving spindle so that the total vertical force
that at least one set of working sieves be obtained, identified,
on the balls as a result of the weights, shaft, top grinding ring,
andusedexclusivelyforHGIdeterminationsandthatonlythis
and gear is equal to 29.0 6 0.2 kg (64 6 0.5 lb). The machine
exclusive set of sieves be used.
is equipped with a counter and automatic device which can be
NOTE 1—Excessive wear may be indicated by poor repeatability or by
properly adjusted for stopping the machine after 60 6 0.25
failureofqualitycontrolchecks(8.1.1)toagreereasonablywiththeinitial
revolutions.
calibration data.
4.8.1 Thepositionofthecountertripmechanismbeforeand
4.5.2 Normal wear on sieves is compensated by the use of
after the test must be used to determine the number of
proper standard reference samples (SRSs) and proper calibra- revolutions completed. Sometimes, it may be necessary to
tion of equipment; excessive wear such as holes or tears in the position strategically the counter trip mechanism at the begin-
sieve cloth, and so forth is not compensated by SRSs. Because ning of the test to accomplish the desired number of revolu-
excessive wear is unacceptable, inspect sieves carefully before tions(thatis,watchwherethetripmechanismisinitially,count
each test to ensure the absence of excessive wear. For the 75- the number of revolutions from the point of origin, determine
and 600-µm (No. 200 and 30) sieves, use only a soft-bristled where the trip mechanism is at the end of the test, and
brush (such as short-bristled camel hair) for brushing and determine if the specified 60 6 0.25 revolutions are obtained.
cleaning. If not, adjust the position of the trip mechanism at the
beginning of the test until the specified number of revolutions
NOTE 2—Itisgoodpracticetokeepaseparateprimary75-µm(No.200)
are obtained).
check sieve to be used only to check the 75-µm working sieve described
in 4.5.1 when the working sieve becomes suspect. This check is done by
runningacomparativeHGItestbetweenthetwo75-µmsieves.Useofthe 5. Standard Reference Samples (SRSs) for Calibration
workingsieveforHGIsshouldbediscontinuedifHGIdifferencebetween
5.1 Four SRSs prepared especially for this purpose (in
the sieves is greater than 1 HGI unit.
accordance with Annex A1) and representing grindability
4.6 Crusher—A laboratory plate mill capable of reducing
indices of approximately 40, 60, 80, and 100 shall be used for
4.75-mm (No. 4) sieve size coal particles with the production
calibration. (See Section 8.)
of a minimum of minus 600-µm (minus No. 30) sieve size
material (Note 3). The crusher plates shall be serrated and
about 100 mm (4 in.) in diameter (Note 4). The distance
D05.07 Minutes, J. Gardner, Georgia Power and G. Linton, October 1990.
betweentheplatesshallbeadjustable,andtherelativespeedof
Primary standard reference samples are available from The Pennsylvania State
rotation of the plates shall not exceed 200 r/min.
University,RonaldS.WascoTheEnergyInstitute,C-211CUL,UniversityPark,PA
16802, Telephone: 814-863-5384, Fax: 814-863-7432, email: rxw19@psu.edu,
NOTE 3—Evidence from HGI standard reference sample user-response
www.energy.psu.edu/HGI. ASTM Subcommittee D05.07 and the ASTM/DOE
forms (8.4) indicates that the median value of percent recovery of the
Liaison Task Group maintain oversight for production of only the primary standard
4.75-mm (No. 4) material as 1.18-mm by 600-µm (Nos. 16 by 30)
reference samples. Secondary standard reference samples are available from other
material, regardless of the HGI level, is about 55%. sources.
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D409–02 (2007)
FIG. 1 Hardgrove Grindability Machine
5.1.1 Upon receipt, each of the SRSs should be examined Method D2013 except that the sample topsize shall not be
for the following: reduced beyond the 4.75-mm (No. 4) sieve, and the sample
5.1.1.1 Preparation date (no more than six months old). shall weigh at least 1000 g.
5.1.1.2 Oversize (material retained on a 4.75-mm (No. 4)
sieve).[Lessthan5%+4.75mmandnoparticleona6.30-mm
7. Preparation of Test Samples
( ⁄4-in. square-holed sieve).] (See 7.3.)
7.1 Prepare a 1.18-mm 3600-µm (No. 16 3No. 30) test
5.1.1.3 Foreign, noncoal material (no wood, rock, slate, and
sampleforestablishingtheHGIofSRSs,forcalibration,orfor
so forth).
routine determination of HGI.
5.1.1.4 Excessive fines (−600-µm (−No. 30) material) (less
7.2 Whennecessary,dividethequantityof4.75-mm(No.4)
than 30%). (See 7.3.)
sieve size coal to not less than 1000-g lots using an enclosed
5.1.2 When any of these parameters are unacceptable,
riffle, and air dry each sample in conformance with Method
contact the agency responsible for production of the SRSs and
D2013.
report the data on the response form accompanying the SRSs
7.3 Sieve the entire amount (1000 g) of air-dried 4.75-mm
(see 8.4).
(No. 4) sieve size sample in lots of no greater than 250 g, for
6. Gross Samples
2 min 6 10 s in the mechanical sieving machine. Use a set of
6.1 Collect a gross sample of coal, representative of the nested sieves consisting of a 1.18-mm (No. 16) sieve on top of
a 600-µm (No. 30) sieve. [It may be appropriate to include a
material from which it is taken, in accordance with Practice
D2234/D2234M, and prepare the sample in accordance with 4.75-mm (No. 4) and a 2.36-mm (No. 8) sieve in this nest of
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D409–02 (2007)
8.2 For each calibration, process four standard reference
samples with indices of approximately 40, 60, 80, and 100
separately as described above. Process the samples as outlined
below(Section9),andusetheresultstodeterminetheequation
ofthelinebyuseofthesumofleastsquaresmethod(8.3)and,
if desired, to prepare a calibration chart (8.3.1).
8.3 Bythemethodofthesumofleastsquares,determinethe
equation of the line that best fits the analytical results obtained
from the four HGI SRSs. An example HGI calculation from
SRS data, shown in Table 1, illustrates this method.
8.3.1 Example—SumofLeastSquaresFit—Theequationof
the line for the sum of least squares takes the form of:
Y 5 a 1 bX (1)
where:
Y = HGI,
a = y axis intercept,
b = slope of the regression line, and
X = calculated−75-µm (−No. 200) material.
a and b can be determined by use of the following table and
equations:
YX X XY
40 4.35 18.92 174.00
FIG. 2 Grinding Elements of Hardgrove Machine
58 7.14 50.98 414.12
83 10.44 108.99 866.52
100 13.38 179.02 1338.00
(Y = 281 (X = 35.31 ((X ) = 357.91 ((XY ) = 2792.64
sieves to record the particle size distribution and the topsize of
the sample.] Weigh and record the mass of each sieve size. (Y(X 2 (X(XY
a 5 (2)
2 2
7.4 Stage crush the material retained on the 1.18-mm (No. n(X 2 ~(X!
16) sieve with the crusher adjusted so that only the largest
particles are crushed. Take the crushed material in lots no
n(XY 2 ( X(Y
b 5 (3)
2 2
greaterthan250gandsievefor2min 610sinthemechanical
n(X 2 ~(X!
sieving machine. Return the oversize to the crusher, after
settingthecrushersothatonlythelargestparticlesarecrushed.
where:
Continue the stage crushing and sieving procedure until all the
(Y = 281,
material passes the 1.18-mm sieve. Retain the 1.18-
(X = 35.31,
mm 3600-µm (No. 16 3No. 30) material.
((X ) = 357.91,
7.5 Mix well all
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