1、Designation: D 4371 06Standard Test Method forDetermining the Washability Characteristics of Coal1This standard is issued under the fixed designation D 4371; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe American Society for Testing and Materials has recognized the need for a standard procedureto conduct washability analyses tha
3、t will serve as an aid to technical communication amongindividuals and organizations that supply, purchase, and utilize coal. This test method standardizesprocedures utilized for performing washability analyses, the data from which can be used forinterpreting preparation plant efficiency, for determ
4、ining preparation plant design, and for determiningthe potential recovery and quality of coal reserves.1. Scope1.1 This test method describes procedures for determiningthe washability characteristics of coarse-coal fractions andfine-coal fractions. Each sample being tested can have morethan one coar
5、se-coal size fraction and more than one fine-coalsize fraction (see Annex A1). Each such size fraction has anupper size limit and a lower size limit, neither of whichoverlaps with the next larger nor smaller size fraction. (SeeTest Method D 4749.)1.2 While, in general, this test method has useful ap
6、plicationin determining the washability characteristics of low-rankcoals, in the strictest sense, it is not necessarily the mosttechnically correct test method to determine washability char-acteristics of low-rank coals because of problems relative to theloss of moisture through drying during sample
7、 preparation andanalysis. Methods that are directly applicable to low-rank coalsare to be developed.1.3 The values stated in SI units are to be regarded as thestandard. The values shown in parentheses are for informationonly.1.4 This standard does not purport to address the safetyconcerns, if any, a
8、ssociated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use. For specific hazard statements, seeSection 8 and Appendix X1.2. Referenced Documents2.1 ASTM Standar
9、ds:2D 2013 Practice for Preparing Coal Samples for AnalysisD 2234/D 2234M Practice for Collection of a Gross Sampleof CoalD 4749 Test Method for Performing the Sieve Analysis ofCoal and Designating Coal SizeD 6883 Practice for Manual Sampling of Stationary Coalfrom Railroad Cars, Barges, Trucks, or
10、StockpilesE11 Specification for Wire Cloth and Sieves for TestingPurposesE 100 Specification for ASTM HydrometersE 126 Test Method for Inspection, Calibration, and Verifi-cation of ASTM HydrometersE 323 Specification for Perforated-Plate Sieves for TestingPurposes3. Terminology3.1 Definitions:3.1.1
11、coal washabilitythe determination of the theoreticallimits for the removal of mineral impurities from coal bybeneficiation processes that rely on specific gravity separa-tions.3.2 Definitions of Terms Specific to This Standard:3.2.1 washability analysis of coalthe analysis of thespecific gravity dis
12、tribution of chemical and physical charac-teristics of coal.3.2.1.1 DiscussionIn this test method, the specific gravityfractions are obtained by subjecting the material being studied1This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke and is the direct responsibility of
13、Subcommittee D05.07 on PhysicalCharacteristics of Coal.Current edition approved Sept. 1, 2006. Published September 2006. Originallypublished as approved in 1984. Last previous edition approved in 1998 asD 4371 91(1998).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact A
14、STM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to a series of solutions, e
15、ach with a discrete specific gravity,that cover the range of specific gravities in question. In the caseof the washability analysis of coal, these solutions are obtainedby the mixing of various organic liquids that are relatively inerttoward the majority of coal types. The distribution, as deter-min
16、ed by the analysis, is affected by the physical condition ofthe sample subjected to the washability analysis, for example,the moisture content and the size content of the material.3.2.2 coarse coalthat portion of a coal sample beingsubjected to a washability study that is larger than a specificprede
17、termined particle size, generally between 2.36 mm (No. 8USA Standard Sieve Series) and 9.5 mm (38 in.) round indiameter.3.2.2.1 DiscussionThis same particle size breakpointshould then be used in subsequent washability studies of thesame material sampled from the same location for the sameapplication
18、. This breakpoint is determined by the analyst or theperson designing the test procedure as the point that best suitsthe application. This coarse-coal fraction may be further sieved(generally by dry-sieving) to produce additional size fractions,each of which is processed through the desired specific
19、 gravitysolutions.3.2.3 fine coalthat portion of a coal sample being sub-jected to a washability study that is smaller than the predeter-mined particle size generally between 2.36 mm (No. 8 USAStandard Sieve Series) and 9.5 mm (38 in.) round in diameter,which is specified in 3.2.2.3.2.3.1 Discussion
20、This same particle size breakpointshould then be used in subsequent washability studies of thesame material sampled from the same location for the sameapplication. This breakpoint is determined by the analyst or theperson designing the test procedure as the point which bestsuits the application. Thi
21、s fine-coal fraction may be furthersieved (generally by wet-sieving) to produce additional sizefractions, each of which is processed through the desiredspecific gravity solutions.3.2.4 float/sinka reference to the physical action thatparticles undergo when immersed in a liquid of a predeter-mined sp
22、ecific gravity.3.2.4.1 DiscussionAseries of float/sink tests is consideredas being synonymous with a washability analysis. A floatfraction or float material is the material or the specific gravityfraction that floats in a certain solution of specific gravityliquids. A sink fraction or sink material
23、is the material or thespecific gravity fraction that sinks in a certain solution ofspecific gravity liquids.4. Summary of Test Method4.1 Procedure ADescribes a washability procedure forcoal fractions composed of particles of coal that are larger thana specified, predetermined size, generally between
24、 2.36 mm(No. 8 USA Standard Sieve Series) and 9.5 mm (38 in.) roundin diameter. These coal fractions will be referred to ascoarse-coal fractions.4.1.1 Each coarse-coal size fraction is independently sepa-rated into two distinct specific gravity fractions by placing thesample into a large tank of suf
25、ficient capacity, for example, 40to 80 L (10 to 20 gal), containing a screen basket insert and asolution of organic liquids adjusted to the required specificgravity. The suspension is stirred gently to assure that allparticles are allowed to either float or sink. The material thatfloats on the solut
26、ion is removed first, followed by the portionof sample that sinks.4.2 Procedure BDescribes a washability procedure forcoal fractions composed of particles of coal that are smallerthan the specified, predetermined size chosen in 4.1. These coalfractions will be referred to as fine-coal fractions.4.2.
27、1 Each fine-coal size fraction is separated into twodistinct specific gravity fractions by placing a portion of thefine-coal sample into a float/sink flask of sufficient capacity, forexample, 2 to 4 L (0.5 to 1 gal), containing a solution oforganic liquids adjusted to the required specific gravity (
28、Note1, Note 2, Note 3, and Note 4). Extreme care must be exercisedto avoid overloading the float/sink flask. This suspension isthen stirred to be certain that each individual particle is allowedto float or sink. The material that floats is removed first bycarefully inserting a stopper into the neck
29、of the flask andpouring the organic solution and float material from the upperportion of the float/sink flask through a filtering medium thattraps the float material. The sink material is then removed andcaptured in a similar manner.NOTE 1A limited number of laboratories are currently using separa-t
30、ory funnels for the separation of fine coal particles having a diameter lessthan one third the diameter of the stopcock port.NOTE 2Some laboratories use centrifugal methods of separatingfine-coal density fractions. Centrifugal methods are not a part of this testmethod. A possible source of informati
31、on is the Bureau of Mines Reportof Investigations 5741 (1),3or the Department of Energy, PittsburghEnergy Technology Center, Coal Preparation Branch, P.O. Box 10940,Pittsburgh, PA 15236.NOTE 3Preparation and adjustment of the organic solutions should bedone in an unrestricted container to allow prop
32、er mixing of the reagentsprior to their introduction into the float/sink flasks.NOTE 4It is a general guide that the depth of the particles floatingshould not exceed three to five times the mean diameter of the particles inthe sample. It is suggested to use 200 g, or less.4.3 Preparation of Test Sam
33、ple, Sieving:4.3.1 The bulk sample should be spread on an imperviousbase, preferably under shelter. The sample should be dried andsieved in accordance with Test Method D 4749, using asuitable range of apertures. (Apertures must conform to Speci-fication E11orE323.)4.3.2 Where it is possible that som
34、e fines agglomerate oradhere to larger particles, it is important that wetsieving beused to ensure that fine material reports to the correct particlesize fraction. However, under normal circumstances whereair-drying has occurred, it should not be necessary to wet-sievethe material larger than 3.15 m
35、m (18 in.).4.3.3 As a practical guide, the presence of minus 75-m(No. 200 USA Standard) material should be minimized,because Brownian movement or molecular interference can bedetrimental to proper and efficient separations. Minus 75-m(No. 200 USA Standard) material can then be processed usingseparat
36、e test procedures. (See, for example, the reference inNote 2.)3The boldface numbers in parentheses refer to the list of references appended tothis standard.D43710624.3.4 When required, material which is larger than thedesired topsize is broken by hand or machine-crushed accord-ing to the topsize req
37、uired, or, if applicable, by simulating therelevant part of the crushing circuit.5. Significance and Use5.1 Although the determination of the washability charac-teristics of coal is not an exact science, this washability testmethod can be used to investigate the cleaning characteristicsof coarse- an
38、d fine-coal fractions. However, especially with thefine-coal fractions, this test method may not be applicable forlow-rank coals for reasons explained in 1.2.5.2 The usefulness of this test procedure and the usefulnessof the results derived from washability testing are directlyrelated to the care ex
39、ercised in developing and following thesampling regime while taking into consideration the desireddegree of precision. For more exacting work, it will benecessary to know the general washability characteristics of thematerial in question. This can be done only through pilottesting as described in 9.
40、6 and Annex A3.5.3 This test method, in conjunction with the advice ofexperts and with knowledge of the particle size analysis (seeTest Method D 4749), is used for the engineering design ofcoal preparation facilities.5.4 This test method is also used to assist in process controland to determine the
41、efficiency of operating preparation plants.5.5 This test method is used in core studies to determine thequality washability characteristics of coal reserves; however, inthese instances the typical mass of raw coal from Table 1 maybe neither applicable nor practical. For this reason, corediameter sho
42、uld be as large as possible and subdivision of thecore section by any means or for any purpose prior towashability testing should be avoided. Care must be exercisedin the design of the coring programs, including the consider-ation of appropriate geostatistics, in order that the potentialrecovery and
43、 quality of the coal reserves, as defined by thewashability analysis of the cores, have any practical signifi-cance.6. Apparatus6.1 The suggested apparatus to be used should be as simpleas possible and be commensurate with the test objectivetheprincipal criteria being that it should be unaffected by
44、 thesolutions involved (that is, the organic liquids do not corrode,etch, or otherwise react with the materials from which theapparatus is constructed) and that it should be convenient foruse (see X1.3). Types of apparatus that have been found to besuitable are discussed in the following subsections
45、 and areillustrated in Fig. 1, Fig. 2, and Fig. 3.6.2 Suitable Float/Sink Container for Coarse-CoalFractionsThe float/sink apparatus may consist of a wiremesh insert and a holding tank (Fig. 1 and Fig. 2). The wiremesh insert should consist entirely of wire mesh, have solidsides with a wire mesh bot
46、tom, or have a solid bottom withwire mesh sides. The wire mesh used must be smaller than onehalf the size of the finest coal in the fraction. The insert fitsinside the holding tank. The insert may have handles attachedor may utilize an overhead lifting device to facilitate removalfrom the tank. A ty
47、pical laboratory holding tank has approxi-mately 40 to 80-L (10 to 20-gal) capacity. Tank and insert mustbe designed so as to be compatible.NOTE 5It is possible that the geometry of the tank may have someeffect on the ease with which the materials are removed from the tank.Square tanks have the foll
48、owing disadvantages: (a) it is difficult to get thewire mesh strainer into the corners to remove all of the float material, and(b) material, especially the sink fraction, may be trapped in the cornerswhile the material is being removed from the tank.6.3 Suitable Float/Sink Flask for Fine-Coal Fracti
49、onsThefloat/sink flasks, that typically have a capacity of 2 to 4 L (0.5to 1 gal), should be constructed with ground glass connectingjoints (see Fig. 3).6.4 Additional Apparatus:6.4.1 Balance, suggested 2000-g capacity, sensitive to 6 0.1g, for weighing small samples or fractions.6.4.2 Balance, suggested 0 to 110-kg (0 to 250-lb) capacity,sensitive to 645 g (0.10 lb) for weighing large samples orfractions.6.4.3 Wire Mesh Strainers, with mesh size one half of thesize of the smallest particle.6.4.4 Vacuum or Pressure Filter, or Filter Funnel for grav-ity filtra
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