Standard Practice for Measuring Fluidization Segregation Tendencies of Powders

SCOPE
1.1 This practice covers an apparatus and procedure for simulating the segregation tendencies of powders by means of the fluidization mechanism.
1.2 Powders must be capable of being fluidized in order to be tested by this practice.
1.3 Temperature- and humidity-sensitive powders may need to be tested at different temperatures and moisture contents, as would happen in an industrial environment. Further, the gas supply (type, temperature, and humidity) should also match the industrial conditions.
1.4 This standard is not applicable to all bulk solids and segregation mechanisms: while fluidization is a common segregation mechanism experienced by many fine powders, other segregation mechanisms not evaluated by this standard might induce segregation in practice.
1.5 The extent to which segregation will occur in an industrial situation is not only a function of the powder and its tendency to segregate, but also the handling equipment (for example, bin design), process (for example, transfer rates), and environment.
1.6 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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Publication Date
31-Dec-2003
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ASTM D6941-04 - Standard Practice for Measuring Fluidization Segregation Tendencies of Powders
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 6941 – 04
Standard Practice for
1
Measuring Fluidization Segregation Tendencies of Powders
This standard is issued under the fixed designation D 6941; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope as Used in Engineering Design and Construction
1.1 This practice covers an apparatus and procedure for
3. Terminology
simulating the segregation tendencies of powders by means of
3.1 Definitions—Definitions of terms used in this test
the fluidization mechanism.
method shall be in accordance with Terminology D 653.
1.2 Powders must be capable of being fluidized in order to
3.1.1 fluidization, n—the state in which a powder exhibits
be tested by this practice.
fluid-like properties.
1.3 Temperature- and humidity-sensitive powders may need
3.1.2 fluidization segregation, n—a mechanism that causes
to be tested at different temperatures and moisture contents, as
vertical segregation, that is, horizontal layering of fine and
would happen in an industrial environment. Further, the gas
coarse particles, as resulting from fluidization of the bulk solid.
supply(type,temperature,andhumidity)shouldalsomatchthe
3.1.3 segregation, n—a process through which blended or
industrial conditions.
uniform powders or bulk solids become non-uniform, with
1.4 This standard is not applicable to all bulk solids and
regions of varying composition, for example, particle size.
segregation mechanisms: while fluidization is a common
3.2 Definitions of Terms Specific to This Standard:
segregation mechanism experienced by many fine powders,
3.2.1 high flow-rate, n—the first stage flow-rate used to
other segregation mechanisms not evaluated by this standard
initiate fluidization.
might induce segregation in practice.
3.2.2 hold time, n—the time for which the Low Flow-rate is
1.5 The extent to which segregation will occur in an
held.
industrial situation is not only a function of the powder and its
3.2.3 low flow-rate, n—the second stage flow-rate used to
tendency to segregate, but also the handling equipment (for
maintain fluidization.
example, bin design), process (for example, transfer rates), and
3.2.4 ramp time, n—the time during which the airflow is
environment.
reduced from the Low Flow-rate to zero.
1.6 This standard does not purport to address all of the
3.2.5 representative sample, n—a quantity of the bulk solid
safety concerns, if any, associated with its use. It is the
to be tested that is representative of that solid in an industrial
responsibility of the user of this standard to establish appro-
application being studied. Parameters of interest that may
priate safety and health practices and determine the applica-
affect whether or not a sample is representative include:
bility of regulatory limitations prior to use.
moisture, particle size distribution, raw material variation,
2. Referenced Documents method of production, aging, chemical composition.
2
2.1 ASTM Standards:
4. Summary of Practice
D 653 Terminology Relating to Soil, Rock, and Contained
4.1 A representative sample of a powder is placed in the
Fluids
apparatus.
D 3740 Practice for Minimum Requirements for Agencies
4.2 Pressurizedgas(usuallyair)isblownfromthebottomat
Engaged in the Testing and/or Inspection of Soil and Rock
a series of flow-rates for specified times, creating a state of
fluidization of the powder.
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This practice is under the jurisdiction of ASTM Committee D18 on Soil and 4.3 Once the airflow is stopped, the powder in the test
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization
chamber is divided into three samples from the bottom, center,
and Handling of Powders and Bulk Solids.
and top of the column.
Current edition approved Jan. 1, 2004. Published February 2004. Originally
4.4 The samples are then available to be tested for differ-
approved in 2003. Last previous edition approved in 2003 as D 6941–03.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ences relevant to the application, for example, particle size or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
chemical assay.
Standardsvolume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6941–04
provides a means of evaluating some of those factors.
5. Significance and Use
Practice D 3740 was developed for agencies engaged in the testing
5.1 Fluidization segregation can cause vertical segregation
and/or inspect
...

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