ASTM D5114-90(2010)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5114 − 90 (Reapproved 2010)
Standard Test Method for
Laboratory Froth Flotation of Coal in a Mechanical Cell
This standard is issued under the fixed designation D5114; 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.
INTRODUCTION
Froth flotation of coal, the separation of ash-bearing minerals from combustibles via differences in
surface chemistry, has been steadily increasing in use as a means to treat 600-µm (No. 30 U.S.A.
Standard Sieve Series) or finer coal.The process is one in which many variables need to be monitored
and regulated. Because of this complexity, rigorous laboratory testing is difficult to standardize.
This test method outlines the types of equipment and procedures to apply on a laboratory scale to
isolate key process variables and minimize the variations associated with the design and execution of
a froth flotation test. The objective of the test method is to develop a means by which repeatable
grade/recovery results are ascertained from froth flotation testing of coal without imposing
unnecessary limitations on the applicability of the test results in coal preparation practice.
It is recognized that sample preparation, particularly comminution, has a significant impact on froth
flotation response. This test method does not attempt to define sample preparation and size reduction
practices as part of a froth flotation testing program.
Thistestmethodalsodoesnotcompletelycoverspecificproceduresfortheinvestigationofflotation
kinetics. Such a test is specialized and is highly dependent upon the end use of the data.
1. Scope consistent baseline can be established against which full-scale
performance can be compared.
1.1 This test method covers a laboratory procedure for
conducting a single froth flotation test on fine coal (that is, 1.5 The values stated in either SI units or inch-pound units
nominal top size of 600 µm (No. 30 U.S.A. Standard Sieve are to be regarded separately as standard. The values stated in
Series) or finer) using a defined set of starting point conditions each system may not be exact equivalents; therefore, each
for the operating variables. system shall be used independently of the other. Combining
values from the two systems may result in non-conformance
1.2 This test method does not completely cover specific
with the standard.
procedures for the investigation of flotation kinetics. Such a
1.6 This standard does not purport to address the safety
test is specialized and highly dependent upon the objective of
concerns, if any, associated with its use. It is the responsibility
the data.
of the user of this standard to establish appropriate safety and
1.3 Since optimum conditions for flotation are usually not
health practices and determine the applicability of regulatory
found at the specified starting points, suggestions for develop-
limitations prior to use.
mentofgrade/recoverycurvesaregiveninAppendixX1.Such
1.7 Material Safety Data Sheets (MSDS) for reagents used
a procedure is very case-specific and involves running a series
are to be obtained from suppliers who are to be consulted
of flotation tests in which some of the operating variables are
before work with any chemicals used in this test method.
changed in order to optimize conditions for either yield or
grade.
2. Referenced Documents
1.4 Laboratoryflotationresultsneednotberepresentativeof
2.1 ASTM Standards:
the flotation response of coal in full-scale situations, but a
D121 Terminology of Coal and Coke
D2013 Practice for Preparing Coal Samples for Analysis
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, 2010. Published January 2011. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1990. Last previous edition approved in 2004 as D5114 – 90 (2004). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D5114-90R10. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5114 − 90 (2010)
D2015 Test Method for Gross Calorific Value of Coal and 3.2.10 mechanical cell—atypeofflotationcellthatemploys
Coke by the Adiabatic Bomb Calorimeter (Withdrawn mechanical agitation of a pulp by means of an immersed
2000) impeller (rotor) and stator stirring mechanism. Aeration to the
D2234/D2234M Practice for Collection of a Gross Sample cell can be from an external pressurized air source or self-
of Coal induced air.
D3173 Test Method for Moisture in the Analysis Sample of
3.2.11 natural pH—the measured pH of the pulp prior to the
Coal and Coke
addition of collector, frother, or any conditioning agents.
D3174 Test Method forAsh in theAnalysis Sample of Coal
3.2.12 pulp—afluidmixtureofsolidsandwater,alsoknown
and Coke from Coal
as slurry.
D3177 Test Methods forTotal Sulfur in theAnalysis Sample
3.2.13 recovery—the percent of the valuable component
of Coal and Coke (Withdrawn 2012)
(that is, Btu or combustible) from the feed that reports to the
D4239 Test Method for Sulfur in the Analysis Sample of
froth concentrate product.
Coal and Coke Using High-Temperature Tube Furnace
Combustion 3.2.14 solids concentration—the ratio, expressed as a
D4749 Test Method for Performing the Sieve Analysis of percent, of the weight (mass) of solids to the sum of the weight
Coal and Designating Coal Size
of solids plus water.
3.2.15 tailings—the underflow product from coal froth flo-
3. Terminology
tation.
3.1 Definitions—For definitions of terms used in this test
3.2.16 yield—the weight percent of the feed that reports to
method, see Terminology D121.
the concentrate.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 collector—a reagent used in froth flotation to promote
4. Significance and Use
contact and adhesion between particles and air bubbles.
4.1 This test method uses specific starting point conditions
3.2.2 combustibles—the value obtained by subtracting the
for the froth flotation response to accomplish the following:
dry weight (in percent) of the ash (as determined in Test
4.1.1 Assess responses of one or more coals or blends of
Method D3174) from 100 % representing the original weight
coal, and
of the analyzed sample.
4.1.2 Evaluate and determine froth flotation circuit perfor-
3.2.3 concentrate—the froth product recovered in coal froth mance.
flotation.
5. Apparatus
3.2.4 conditioning agents—all chemicals that enhance the
performance of the collectors or frothers. Conditioning agents
5.1 Laboratory Flotation Machine,withaminimumvolume
change the characteristics of the surface of the minerals or the
of 2 L and a maximum volume of 6 L. Fig. 1 schematically
environment.There are many subgroups according to function:
activators, depressants, emulsifiers, dispersants, flocculants,
chelating reagents, froth depressants, pH modifiers, and so
forth.
3.2.5 flotation cell—the vessel or compartment in which the
flotation test is performed.
3.2.6 froth—a collection of bubbles and particles on the
surface of a pulp in a froth flotation cell.
3.2.7 froth flotation—a process for cleaning fine coal in
which hydrophobic particles, generally coal, attach to air
bubbles in a water medium and rise to the surface to form a
froth. The hydrophilic particles, generally the ash-forming
matter, remain in the water phase.
3.2.8 frother—a reagent used in froth flotation to control the
size and stability of the air bubbles, principally by reducing the
surface tension of water.
3.2.9 grade/recovery—the relationship between quality and
quantity of the clean coal product. The quality can be defined
in terms of ash, sulfur, or Btu content. The quantity can be
designated as yield or heating value recovery (Btu or combus-
tibles).
The last approved version of this historical standard is referenced on
www.astm.org. FIG. 1 5.5-L Mechanical Paddle Laboratory Froth Flotation Cell
D5114 − 90 (2010)
depicts a batch mechanical flotation cell which can be used in 7. Flotation Conditions
conjunction with this test method. The major criterion is that
7.1 The conditions under which a test program is conducted
the unit must be able to provide for constant mechanical
will be systematically varied to generate grade/recovery curves
removal of froth from the cell. In addition, the laboratory unit
(Appendix X1). Table 1 outlines recommended starting point
must have some means of automatic liquid level control.
conditions for a single laboratory-scale test. These conditions
5.1.1 An example of a mechanical paddle laboratory froth
are for laboratory testing parameters and are not designed to
flotation apparatus is shown in Fig. 1. The froth paddles are
simulate in-plant operating conditions that can be highly
rotated at approximately 30 r/min, thus avoiding variation
variable, such as water temperature and chemistry.
caused by manual removal of froth. The froth paddle shall not
7.2 Slurry Temperature—Theoperatingtemperatureshallbe
rotate below the pulp surface and not more than 6 mm ( ⁄4 in.)
22 6 5°C (72 6 9°F).
abovethepulplevel.Thedistancebetweentheoverflowlipand
the edge of the froth paddle shall be at least 3 mm ( ⁄8 in.) but 7.3 Water—Plant, tap, or distilled water may be used,
not more than 6 mm ( ⁄4 in.). whichever is consistent with the object of the test. The source
of water must be recorded.
5.1.2 Thepulpinthecellismaintainedataconstantlevelby
a small tank with an overflow at precisely the desired level to
7.4 Solids Content—The solids content corresponds with
be maintained in the flotation cell.
thatoftheindustrialpreparationplantslurry,iftheobjectofthe
test is to simulate plant conditions. Otherwise, an 8 % solids
NOTE 1—Another suitable slurry level control system consists of a
resistance type level probe, a resistance sensor relay, a solenoid valve, and concentration shall be used.
associated connecting wires. The level probe is mounted inside the cell
7.5 Pulp Level—Maintain between 12.7 and 15.9 mm (0.50
and is connected to the resistance relay which operates the solenoid valve.
and 0.62 in.) below the lip of the cell as measured with the air
When the slurry level drops below the tip of the probe, the relay energizes
thesolenoidvalve.Then,makeupwaterflowsintothecell.Whenthelevel
on and stirrer operating.
rises up to the probe, the solenoid valve is de-energized, which stops the
7.6 Wetting of Coal—Before the addition of reagents and
makeup water flow.
subsequentflotation,itisimportanttoensurethattheproperair
5.2 pH Meter, sensitive to 0.1 units.
bubble attachment can take place at the coal-water interface.
5.3 Timing Device that displays cumulative minutes and Wetting is accomplished in the cell by running the impeller at
seconds. the r/min specified for the flotation step with the air off.
Perform this step for 5 to 10 min before reagent addition. If the
5.4 Air Flow Meter.
sample is in slurry form this wetting step is not necessary.
5.5 Microsyringes or Pipets.
7.7 Reagent Addition—Collector, frother, conditioning
5.6 Balances, with a readability of at least 0.5 % of the total
agent, or any combination thereof shall be governed by the
weight. requirements of the test. Add reagents to the coal slurry and
conditiontoensureproperdistributionofreagents.Conductthe
5.7 Vacuum or Pressure Filter, or a filter funnel for gravity
conditioning step at the same impeller speed as the flotation
filtration.
step with the air flow off.
5.8 Drying Oven with forced air, capable of maintaining a
7.7.1 Add the reagents using either a calibrated microsy-
maximum temperature of 40°C (104°F) and meeting the
ringe or a pipet.
requirements of Method D2013.
7.8 Air Flow—Rate shall be measured and recorded.
5.9 Rinse Bottle.
7.9 Impeller Speed—The starting speed shall be 1200 r/min.
6. Sample Preparation NOTE 2— Impeller speed is an important variable and should be
investigated during optimization, depending on the object of the test.
6.1 The sample history, moisture content, alteration of the
inherent moisture, or alteration of the surface properties have
8. Procedure
considerableeffectontheflotationcharacteristicsofthecoal.It
8.1 Calculate the total mass of coal required for the number
is important that all samples used in flotation testing are stored
offlotationtestsbasedonthemeasuredcellvolumeandthetest
and handled so as to minimize alteration of the surface
solids content.
properties. The origin and history of the sample should be
recorded. It is imperative that all samples be prepared in a
8.2 Divide the total mass into representative portions by
similar manner. Since the generation of grade/recovery curves riffling, in accordance with Method D2013. A few small
will involve several individual tests, sample subdivision and
increments, totalling no more than 15 % of the total mass, may
preparation must be carefully performed to ensure that each be either taken from the subsample or added to the subsample
subsample is representative of the original whole sample. in order to obtain the exact weight.
8.3 Determine the particle size distribution of one of the
portions from 8.2 in accordance with Test Method D4749.
A suitable cell, available from WEMCO, 1796 Tribute Rd., Sacramento, CA
8.4 Rinse the cell thoroughly with water.Add from one half
95815, or equivalent can be used.
totwothirdsofthetotalrequiredwatertothecell.Confirmthat
A suitable slurry level control system, available from C&R Technology, Inc.,
P.O. Box 114, Fall Branch, TN 37656, or equivalent can be used. the air is turned off. Turn the impeller on and adjust to the
D5114 − 90 (2010)
TABLE 1 Starting Point Conditions for Laboratory Froth Flotation
9. Calculation
of Coal
9.1 Calculate all parameters on a dry basis.
NOTE 1—Additional time can be required for a slowly responsive coal;
9.2 Calculate yield, Y, in weight percent as follows:
record any extra time.
Solids concentration 8 % solids 100 3W
c
Y 5
Total volume 2 to 6 L
W 1W
c t
Wetting time 5 min
pH natural
where:
Impeller speed 1200 r/min
Reagent additions and conditioning times: W = weight of froth concentrate, and
c
1. Add collector
W = weight of tailing.
t
2. Condition for 90 s
3. Add frother 9.3 Calculate the percent recovery, A, of any analytical
4. Condition for 30 s
parameter using the following formula, which uses th
...