1、Designation: D 2797/D2797M 09Standard Practice forPreparing Coal Samples for Microscopical Analysis byReflected Light1This standard is issued under the fixed designation D 2797/D2797M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers laboratory procedures for thepreparation of granular samples of bituminous coal and
3、 anthra-cite samples for examination with a microscope using reflectedlight illumination. It does not apply to the preparation oforiented blocks of coal.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be e
4、xact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address the safetyconcerns associated with its use. It is the responsibility of theuser of this
5、standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 2013 Practice for Preparing Coal Samples for AnalysisD 2234/D 2234M Practice for Collection of a Gross Sampleof CoalD 2798
6、 Test Method for Microscopical Determination ofthe Vitrinite Reflectance of CoalD 2799 Test Method for Microscopical Determination ofthe Maceral Composition of CoalD 4596 Practice for Collection of Channel Samples of Coalin a MineE11 Specification for Woven Wire Test Sieve Cloth andTest Sieves3. Sum
7、mary of Practice3.1 Arepresentative sample is crushed to a specified particlesize, air-dried, mixed with a binder, and formed into a briquet.The briquet is then polished to a flat, scratch-free surface forexamination by vertical illumination.4. Significance and Use4.1 Briquets of granular bituminous
8、 coals and anthraciteprepared in accordance with the laboratory procedures of thispractice will have flat, scratch-free surfaces suitable for exami-nation with a microscope using reflected light illumination.The polished surfaces of briquettes prepared by this practicewill contain particles represen
9、tative of the original grosssample.4.2 Samples prepared by this practice are used for micro-scopical determination of the reflectance of the organic com-ponents in a polished specimen of coal (Test Method D 2798)and for microscopical determination of the volume percent ofphysical components of coal
10、(Test Method D 2799).5. Apparatus5.1 Grinder, Pulverizer, or Mill, for final crushing of thesample to pass a 850-m (No. 20) sieve. Mortar and pestle orother equipment suitable for reducing the particle size of a250-g sample that already passes a 4.75-mm (No. 4) sieve untilall of it passes a 850-m (N
11、o. 20) sieve (see 6.5).5.2 Coarse Riffle Samplera riffle with at least twelvedivisions of not less than 12.7 mm 12 in. and not greater than19.1 mm 34 in.5.3 Fine Riffle Samplera riffle with at least twelve divi-sions of not less than 3.2 mm 18 in. and not greater than 6.4mm 14 in.5.4 Sievesa 4.75-mm
12、 (No. 4) and a 850-m (No. 20) U.S.Standard Sieve (Specification E11).5.5 Moldscontainers to hold the coal binder mixture whilethe binder hardens.5.5.1 The mold shall be capable of withstanding pressuresup to 70 MPa 10 000 psi, and shall be made of separable partsso that the briquet can be ejected af
13、ter it has hardened.5.5.2 The mold shall be large enough to provide a plane areaof4cm2or more on one side of the briquet. (Designs ofsuitable 25-mm 1-in. and 32-mm 114-in. inside-diametermolds are shown in Fig. 1).5.6 Hydraulic Pressa press that is capable of producing apressure up to 35 MPa 5000 ps
14、i on the briquet, and has anattachment to eject the briquet after solidification of the binder.1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of Subcommittee D05.28 on PetrographicAnalysis of Coal and Coke.Current edition approved Sept
15、. 1, 2009. Published September 2009. Originallyapproved in 1969. Last previous edition approved in 2007 as D 2797 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to
16、 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.5.7 Grinding and Polishing Equipmentone or several lapson which the coal briquet can be ground and polished to a flat,scratch-fre
17、e surface. Laps may be made of aluminum, iron,brass, bronze, lead, glass, wax, or wood. For notes on grindingand polishing practices, see Appendix X1.NOTE 1Equipment that has 203-mm 8-in. diameter disk laps,gear-driven at 160 to 170 r/min, and that has an automatic sample holderattachment is recomme
18、nded.5.8 Sample Cleanersome equipment is essential forcleaning coal briquets between the different grinding or pol-ishing stages. This may be a simple stream of water or an airjet, but an ultrasonic cleaner is recommended.5.9 Containersif samples are to be transported or storedbefore briquets are pr
19、epared, glass jars, bottles, or metal canshaving tight-fitting closures shall be used. Metal cans shallhave plastic liners.6. Materials6.1 BinderAny binding material fulfilling the followingrequirements may be used for preparing the coal briquet:6.1.1 The binder shall hold all coal particles securel
20、y duringgrinding, polishing, and observing the sample.6.1.2 The binder and the hardening process used shall notreact with the coal or the atmosphere or expose the coal tothermal oxidation.6.1.3 Under the microscope, the binder shall contrast mark-edly with constituents being measured when immersed i
21、n oilhaving an index of refraction of about 1.518.6.1.4 The binder shall be such that a substantially flat andscratch-free surface can be obtained as a result of the grindingand polishing procedure.NOTE 2Relief, or difference in level, particularly between the coaland the binder, is undesirable for
22、reflectance determination. Althoughrelief depends a great extent on the polishing technique, use of a binderwith a hardness comparable to that of the coal is very helpful.NOTE 3Various types of epoxy resisns and heat-setting powders aresuitable as a binder.6.2 Release AgentAny preparation that does
23、not damagethe molds or adversely affect the coal or mounting mediummay be used to coat the inside of the mold and facilitateejection of the briquet.6.3 Grinding AbrasivesWater-resistant, adhesive-backedsilicon carbide papers of grit Nos. 240, 320, 400, and 600. Twoor three of these are used accordin
24、g to a plan such as one ofthose listed in Table 1.6.4 Polishing AbrasivesAluminum oxide powders of 3-,1-, 0.3-, 0.1-, and 0.05-m sizes. Two or three of these are usedaccording to a plan such as one of those listed in Table 1.6.5 Lap CoveringsNap-free cloths of cotton and silk, andchemotextile materi
25、al backed with water-resistant adhesive.6.6 DetergentAny nonoxidizing detergent may be usedfor cleaning briquets after each grinding or polishing stage.7. Sampling7.1 Obtain samples of coal in accordance with PracticeD 2234/D 2234M and Practice D 4596, when appropriate.NOTE 1Material: cold rolled or
26、 stainless steel. Dimensions a and b(inside diameters) are nominally 32 mm 114 in. and 25 mm 1 in. If anautomatic polishing attachment is to be used, these dimensions should bespecified to yield a briquet fitting snugly in the briquet holder.FIG. 1 Molds Suitable for Briquetting Coal SamplesTABLE 1
27、Suggested Abrasive Sequences for Grinding and Polishing of BriquetsGrinding With Silicon Carbide Paper Polishing with Alumina on Fabric SupportPlanNo.Stage 1 Stage 2 Stage 3 Stage 1 Stage 2 Stage 31 240 grit 400 grit 600 grit 3 m on chemotextile 0.05 m on one or twolayers of silk cloth overchemotext
28、ile.2 400 grit 600 grit . 0.3 m on chemotextile 0.05 m on silk cloth aloneor on silk cloth overcotton cloth.3 240 grit 400 grit . 0.3 m on chemotextile 0.05 m on cotton clothover chemotextile.4 320 grit 600 grit . 3 m on chemotextile 0.1 m on silk cloth overchemotextile.5 400 grit 600 grit . 1 m on
29、two layers ofcotton cloth0.3 m on three layers ofcotton cloth0.05 m on silk cloth over twolayers of cotton clothD 2797/D2797M 0927.2 If the coal sample has not previously been air dried,bring the sample to room conditions by exposure to thelaboratory atmosphere.7.3 Crush and divide the gross sample
30、in accordance withPractice D 2013 to obtain a representative 2.36 mm (No.8 )sieve size subsample (Note 4). Divide to a minimum weight of500g (for cleaned coal) or 1000g (for unknown or all othercoals.)NOTE 4The terms gross sample and subsample are defined, and thequality and amount of the subsample
31、are specified in Practice D 2013.7.4 Stage crush or grind the 2.36 mm (No. 8) sieve sizesubsample to pass through a 850 m (No. 20) sieve in a mannerthat minimizes the production of excessive fines. This isaccomplished by successive sieving with intermittent grindingof the oversize coal for short per
32、iods until all coal passes thespecified size. A mortar and pestle, adjustable plate mill, orother apparatus and procedures are acceptable if production offines is minimized.7.5 Riffle the 850 m (No. 20) sieve size coal to 250 g andstore in a container that meets the requirements in 5.9.Noadditional
33、crushing or grinding is required.7.6 Pass the 850 m (No. 20) sieve size coal through the fineriffle sampler (5.3) to obtain the amount of coal needed for oneor two briquets.Approximately 8 to 16 g of coal is adequate forone 25 mm 1-in diameter briquet.7.7 Place the coal in a container (5.9) or proce
34、ed withpreparing the coal briquet.8. Preparation of Coal Briquet8.1 Prepare a coal briquet using a binder that meets therequirements of 6.1 in such a manner that, when polished, atleast 60 % of the cross-sectional area will be coal.8.1.1 Add activator or hardener, in the amount recom-mended by the s
35、upplier, to about4goftheepoxy resin for each10 g of coal. Mix thoroughly with a spatula or disposablewooden stirring stick. Place the riffled coal sample in a suitablesmall container. Thoroughly stir a few drops of resin into thecoal sample. Continue to add resin, a few drops at a time, andstir unti
36、l all coal particles are wetted and the coal-resin mixturecoheres when pressed to the side of the container with thespatula.8.1.2 Coat the internal surfaces of a mold (including plung-ers) with a release agent and insert the lower plunger. Fill themold with the coal-resin mixture. Insert the upper p
37、lunger,place the mold in a hydraulic press, and apply a pressure of 28to 35 MPa 4000 to 5000 psi on the briquet for 3 to 5 s.Release and reapply the pressure; repeat this cycle about 15times.NOTE 5The repeated application and release of pressure removes airbubbles introduced when the coal is mixed w
38、ith the resin.8.1.3 Allow the briquet in the mold to harden adequately forpolishing. Overnight at room temperature acceptable. Heatingthe briquet at elevated temperatures in an oven is acceptable ifthe procedure meets requirements in 6.1.2.8.1.4 Eject the coal briquet from the mold using the special
39、attachment on the press and label the briquet.9. Preparation of Briquet Surface9.1 Grind and polish one of the base surfaces of the briqueton a lap to obtain a surface suitable for microscopical exami-nation. Grinding and polishing may be done either by handmanipulation or with an automatic attachme
40、nt. Use a series ofabrasives of decreasing particle size according to a plan such asone of those described in Table 1. The surface so obtained shallmeet the following requirements:9.1.1 Enough material shall be removed from the briquet toproduce a flat surface over the entire area.9.1.2 The surface
41、shall be free of pits caused by loss ofgrains of coal constituents or mineral matter.9.1.3 The surface shall be substantially free of scratcheswhen examined at a magnification of 6003 or more under oilimmersion.9.1.4 The surface shall be substantially free of relief.9.1.5 The coal macerals shall be
42、free of charring andsmearing.9.1.6 The surface shall be free of grinding and polishingcompounds.9.2 After each grinding or polishing step, clean the briquetor briquets to remove all abrasive and dislodged mineralparticles. Use of an ultrasonic cleaner filled with water anddetergent is recommended.10
43、. Moisture Control10.1 An experimental test program has determined thatpolished coal briquet surfaces for most coals in the vitrinitereflectance range of 0.6 % to 1.70 % (mean maximum reflec-tance) do not require desiccation prior to measuring reflec-tance310.2 If the vitrinite reflectance is outsid
44、e the range specifiedin 10.1 or it has been established that a particular coal isaffected by water absorption on the polished coal surfacecausing lower reflectance, then desiccate the briquet for 15 hbefore measuring reflectance.NOTE 6During the wet polishing process, some coals absorb moisturethat
45、can affect the amount of light reflected from the coal. In general, thegreater the amount of water absorbed the less the reflectance. Thereflectance of high-volatile C bituminous coal, some high-volatile Bbituminous coals, and anthracite can be affected to varying degrees byabsorption of moisture.3D
46、eVanney, N., “Impact of Sample Desiccation on the Mean Maximum VitriniteReflectance for Various Ranks of Coal”, The Society for Organic PetrologyNewsletter, Vol 18, No. 3, September 2001, pp. 1520.D 2797/D2797M 093APPENDIX(Nonmandatory Information)X1. NOTES ON GRINDING AND POLISHING PRACTICESX1.1 A
47、stream of water is recommended to carry away thecuttings and cool the sample when grinding with the siliconcarbide papers. The objective of the first (coarsest) grindingstep is to obtain a coplanar surface on all briquets and penetratebelow the surface layer of particles. In subsequent grindingsteps
48、, the period should be long enough to remove scratches ofthe preceding step. A grinding time of 15 to 30 s is usually, butnot always, sufficient. (Use of a rotating lap with automaticattachment is assumed here.)X1.2 Room air cleanliness is important in polishing. Airpollutants, if hard (for example,
49、 quartz), can scratch the surfaceor, if soft enough (for example, soot), can smear it.X1.3 Polishing abrasives are usually applied as a slurry indistilled water, diluted so that, on standing, the abrasive settlesto a level constituting 5 to 10 % of the column of mixture.Polishing cloths must be free of all knots, snags, holes, or otherimperfections and should be stretched tightly over the wheel.The amount of load (pressure) applied in polishing is veryimportant. Variation of hardness of vitrinite with coal
