1、Designation: D2797/D2797M 11aStandard Practice forPreparing Coal Samples for Microscopical Analysis byReflected Light1This standard is issued under the fixed designation D2797/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 ex
4、act 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 s
5、tandard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D2013 Practice for Preparing Coal Samples for AnalysisD2234/D2234M Practice for Collection of a Gross Sampleof CoalD2798 Test
6、 Method for Microscopical Determination of theVitrinite Reflectance of CoalD2799 Test Method for Microscopical Determination of theMaceral Composition of CoalD4596 Practice for Collection of Channel Samples of Coalin a MineE11 Specification for Woven Wire Test Sieve Cloth and TestSieves3. Summary of
7、 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 coals
8、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 representative
9、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 D2798)and for microscopical determination of the volume percent ofphysical components of coal (Test Me
10、thod D2799).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 (No. 20) si
11、eve (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 (No. 4)
12、and a 850-m (No. 20) U.S.Standard Sieve (Specification E11).5.5 Moldscontainers to hold the coal binder mixture whilethe binder hardens.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 Co
13、al and Coke.Current edition approved June 1, 2011. Published July 2011. Originally approvedin 1969. Last previous edition approved in 2011 as D2797 11. DOI: 10.1520/D2797_D2797M-11A.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.o
14、rg. 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.5.5.1 The mold shall be capable of withstanding pressuresup to 7
15、0 MPa 10 000 psi, and shall be made of separable partsso that the briquet can be ejected after 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
16、. 1).5.6 Mounting Pressa manual or automated press that iscapable of producing a pressure up to 35 MPa 5000 psi on thebriquet, and has an attachment to eject the briquet aftersolidification of the binder.Aheat-setting automated press shallbe used with an appropriate thermoset binder.5.7 Grinding and
17、 Polishing Equipmentone or several lapson which the coal briquet can be ground and polished to a flat,scratch-free surface. Laps may be made of aluminum, iron,brass, bronze, lead, glass, wax, or wood. Equipment that has203-mm 8-in. diameter disk laps, gear-driven at 160 to 170r/min, and that has an
18、automatic sample holder attachment issuitable. For notes on grinding and polishing practices, seeAppendix X1.5.8 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 ultrason
19、ic cleaner is recommended.5.9 Containersif samples are to be transported or storedbefore briquets are prepared, 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 followingrequir
20、ements may be used for preparing the coal briquet:6.1.1 The binder shall hold all coal particles securely 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 Un
21、der the microscope, the binder shall contrast mark-edly with constituents being measured when immersed in 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 procedur
22、e.6.1.4.1 Relief, or difference in level, particularly betweenthe coal and the binder, is undesirable for reflectance determi-nation. Although relief depends a great extent on the polishingtechnique, use of a binder with a hardness comparable to thatof the coal is very helpful.6.1.4.2 Various types
23、of epoxy resins and heat-setting pow-ders are suitable as a binder.6.2 Release AgentAny preparation that does 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, adh
24、esive-backedsilicon carbide papers of grit Nos. 240, 320, 400, and 600. Twoor three of these are used according 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
25、 as one of those listed in Table 1.6.5 Lap CoveringsNap-free cloths of cotton and silk, andchemotextile material 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
26、in accordance with PracticeD2234/D2234M and Practice D4596, when appropriate.7.2 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 in accordance withPractice D2013 to obtain a represe
27、ntative 2.36 mm (No.8 )sieve size subsample (Note 1). Divide to a minimum weight of500g (for cleaned coal) or 1000g (for unknown or all othercoals.)NOTE 1The terms gross sample and subsample are defined, and thequality and amount of the subsample are specified in Practice D2013.7.4 Stage crush or gr
28、ind 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 periods until all coal passes thespecified size. A mortar
29、 and pestle, adjustable plate mill, orother apparatus and procedures are acceptable if production offines is minimized.NOTE 1Material: cold rolled or 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, t
30、hese dimensions should bespecified to yield a briquet fitting snugly in the briquet holder.FIG. 1 Molds Suitable for Briquetting Coal SamplesD2797/D2797M 11a27.5 Riffle the 850 m (No. 20) sieve size coal to 250 g andstore in a container that meets the requirements in 5.9.Noadditional crushing or gri
31、nding 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 proceed withpreparin
32、g 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 supplier, to abo
33、ut4goftheepoxy 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 until all coal part
34、icles are wetted and the coal-resin mixturecoheres when pressed to the side of the container with thespatula. For thermoset briquettes mix coal and binder togetherin a small container or disposable paper cup in appropriateproportions so the that at least 60 % of the cross sectional baseof the brique
35、tte will be coal.8.1.2 Coat the internal surfaces of a mold or interior of theautomated press mold and fittings (including plungers) with arelease agent and insert the lower plunger. Fill the mold withthe coal-resin mixture. For manual presses, insert the upperplunger, place the mold in a hydraulic
36、press, and apply apressure of 28 to 35 MPa 4000 to 5000 psi on the briquet for3 to 5 s. Release and reapply the pressure; repeat this cycleabout 5 times. The repeated application and release of pressureremoves air bubbles introduced when the coal is mixed withthe resin.8.1.3 For automated presses, p
37、rogram pressures and tem-peratures appropriate to the size and number of briquettesbeing prepared in the mold and type of thermoset binder used.8.1.4 For manual presses, allow the briquet in the mold toharden adequately for polishing. Overnight at room tempera-ture is acceptable. Heating the briquet
38、 at elevated temperaturesin an oven is acceptable if the procedure meets requirements in6.1.2. Briquettes made with thermoset powders require el-evated temperatures as specified by the manufacturer for themounting medium to set.8.1.5 For manual presses, eject the coal briquet from themold using the
39、special attachment on the press and label thebriquet. For automated presses, eject coal briquette when it hascooled.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 polishin
40、g may be done either by handmanipulation or with an automatic attachment. Use a series ofabrasives of decreasing particle size such as those described inTable 1. The surface so obtained shall meet the followingrequirements:9.1.1 Enough material shall be removed from the briquet toproduce a flat surf
41、ace over the entire area.9.1.2 The surface 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
42、of relief.9.1.5 The coal macerals shall be 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 fille
43、d with water anddetergent is recommended.10. 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-tance3
44、3DeVanney, 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.TABLE 1 Suggested Abrasive Sequences for Grinding and Polishing of BriquetsGrinding With Silicon Carbid
45、e 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 overchemotextile.2 400 grit 600 grit . 0.3 m on chemotextile 0.05 m on silk cloth aloneor on silk cloth over
46、cotton 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 two layers ofcotton cloth0.3 m on three layers ofcotton cloth0.05 m on silk cloth over twolayer
47、s of cotton clothD2797/D2797M 11a310.2 If the vitrinite reflectance is outside 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 reflec
48、tance.NOTE 2During the wet polishing process, some coals absorb moisturethat 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,
49、and anthracite can be affected to varying degrees byabsorption of moisture.APPENDIX(Nonmandatory Information)X1. NOTES ON GRINDING AND POLISHING PRACTICESX1.1 A 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, the period should be long enough to remove scratches
