1、Designation:D774312Standard Test Method forMeasuring the Minimum Fluidization Velocities of FreeFlowing Powders1This standard is issued under the fixed designation D7743;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of las
2、t revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method describes the apparatus and procedureneeded for determining the minimum fluidization velocity ofGeldart Group
3、 A powders and the minimum fluidization orcomplete fluidization velocity of Geldart Group B powders.1.1.1 This test method is for powders that are readily oreasily fluidizable and fall into the category of Group A and Bof the“Geldart”classification.The fluidization of GeldartGroup C powders will be
4、addressed in another standard.Thistest method could apply to Geldart Group D particles but thefocus of this document is towards Group and A and Bmaterials.1.1.2 Geldart classification of powders is often defined bycomparing the Sauter mean particle size with the differencebetween the particle densit
5、y and the density of the fluidizinggas,as illustrated in Fig.1(1).21.1.2.1 Group A powders are easily fluidized but there is adifference between the gas velocity where the bed is initiallyfluidized and the velocity where bubbles are first observed.ForGroup A powders,bed expansion can be considerable
6、 beforeany bubbles are observed.Group B powders are also easilyfluidized;but there is no difference between the velocity wherethe bed is fluidized and the velocity at the onset of bubbling.The minimum gas velocity,where all of the particles are fullysupported by the gas for Group B powders,is often
7、referred toas the“complete fluidization velocity”instead of minimumfluidization velocity.Group C powders are cohesive and can bedifficult to fluidize.1.1.2.2 Group A powders can be distinguished from GroupB powders by the response to deaeration.Group A powdersdeaerate relatively slowly whereas Group
8、 B powders deaeratealmost instantaneously in fluidized beds.1.1.2.3 Group A Powders that lie near or on the Group A/Cboundary may be tested by this method.However,if thepowders do not fluidize freely,test results should be consideredinvalid.1.1.2.4 Temperature,moisture(water)content,particle sizedis
9、tribution,particle shape and sometimes other variablesinfluence the Geldart classification of a powder.Deaerationtesting specified in 1.1.2.2 is a more definitive test than simplyusing particle size and density differences as described in 1.1.2.NOTE1A Standard Practice for deaeration testing is unde
10、r develop-ment.1.2 This test method should be performed in a laboratoryunder controlled conditions of temperature and humidity.1.3 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.3.1 The procedures used to specify h
11、ow data are collected/recorded or calculated,in this standard are regarded as theindustry standard.In addition they are representative of thesignificant digits that generally should be retained.The proce-dures used do not consider material variations,the purpose forobtaining the data,special purpose
12、 studies,or any consider-ations for the users objectives;and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations.It is beyond the scopeof this standard to consider significant digits used in analysismethods for engineering design
13、.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.24 on Characterizationand Handling of Powd
14、ers and Bulk Solids.Current edition approved June 1,2012.Published August 2012.DOI:10.1520/D7743-12.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United Stat
15、es1 1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced D
16、ocuments2.1 ASTM Standards:3D653 Terminology Relating to Soil,Rock,and ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture)Content of Soil and Rock by MassD3195 Practice for Rotameter CalibrationD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for Using Significant Digits in GeotechnicalData3.Terminology3.1 Definitions:3.1.1 For common definitions of t
