1、Designation: D 2797 07Standard Practice forPreparing Coal Samples for Microscopical Analysis byReflected Light1This standard is issued under the fixed designation D 2797; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 anthra-cite
3、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 SI units shall be considered asstandard; and inch-pound units shall be considered as approxi-mate equivalents.1.3 This standard does no
4、t purport to address the safetyconcerns associated with its use. It is the responsibility of theuser of this 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
5、 for Preparing Coal Samples for AnalysisD 2234/D 2234M Practice for Collection of a Gross Sampleof CoalD 2798 Test Method for Microscopical Determination ofthe Vitrinite Reflectance of CoalD 2799 Test Method for Microscopical Determination ofthe Maceral Composition of CoalD 4596 Practice for Collect
6、ion of Channel Samples of Coalin a MineE11 Specification for Wire Cloth and Sieves for TestingPurposes3. Summary 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-fre
7、e surface forexamination by vertical illumination.4. Significance and Use4.1 Briquets of granular bituminous 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 lig
8、ht illumination.The polished surfaces of briquettes prepared by this practicewill contain particles representative 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
9、(Test Method D 2798)and for microscopical determination of the volume percent ofphysical components of coal (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
10、 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) 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 wi
11、th 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) 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 wi
12、thstanding pressuresup to 70 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.) insi
13、de-diametermolds are shown in Fig. 1).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 Oct. 1, 2007. Published October 2007. Originallyapproved in 1
14、969. Last previous edition approved in 2004 as D 2797 2004.2For 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 the standards Document Summary page onthe ASTM website.1C
15、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.6 Hydraulic Pressa press that is capable of producing apressure up to 35 MPa (5000 psi) on the briquet, and has anattachment to eject the briquet after solidification of the binder.5.7
16、Grinding and 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. For notes on grindingand polishing practices, see Appendix X1.NOTE 1Equipment that has
17、203-mm (8-in.) diameter disk laps,gear-driven at 160 to 170 r/min, and that has an automatic sample holderattachment is recommended.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
18、airjet, but an ultrasonic 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 fulfill
19、ing the followingrequirements 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 tothe
20、rmal oxidation.6.1.3 Under 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 grindin
21、gand polishing procedure.NOTE 2Relief, or difference in level, particularly between the coaland the binder, is undesirable for 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.NO
22、TE 3An epoxy resin has been found suitable. The resin is com-posed of the diglycidyl ethers of bis-phenol-A and its homologs and isdiluted with butyl glycidyl ether. The resin is used with an activatorcomposed of aliphatic polyamines or their adducts or both. The amount ofactivator is calculated fro
23、m the equation:A 5 100 MA/EH (1)where:A = amount of activator, parts per 100 (by weight) ofresin diluent mixture;MA= molecular weight of activator;E = epoxide equivalent weight of epoxy-diluent mixture;andH = number of active hydrogens per molecular of acti-vator.6.2 Release AgentAny preparation tha
24、t 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, adhesive-backedsilicon carbide papers of grit Nos. 240, 320, 400, and 600. Twoor three of these are used a
25、ccording 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
26、 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 (Note 4) of coal in accordance withPractice D 2234/D 2234M and Practice D 4596, when appro-priate.7.2 If the co
27、al 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 D 2013 to obtain a subsample (Note 4) of either4.75-mm (No. 4) or 2.36-mm (No. 8) sieve size.NOTE 4The terms gross
28、sample and subsample are defined, and thequality and amount of the subsample are specified in Practice D 2013.7.4 Crush oversize particles (if present) of the subsampleuntil all pass a 4.75-mm (No. 4) sieve. Reduce this subsampleby riffling with the coarse riffle sampler to not less than 250 g.NOTE
29、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, these dimensions should bespecified to yield a briquet fitting snugly in the briquet holder.FIG. 1 Molds Suitable for Br
30、iquetting Coal SamplesD2797072Except for the final weight, the procedure shall be in accor-dance with Practice D 2013.7.5 Crush this 250-g subsample until 100 % passes a850-m (No. 20) sieve in a manner such that production offines is minimized. This can be accomplished by stage grinding(successive s
31、ieving with intermittent grinding of the oversizecoal for short periods until all coal passes the specified size)with a mortar and pestle. Other apparatus or procedures that donot produce appreciably more fines may be used.7.6 Pass the sieved coal sample through the fine rifflesampler (5.3) to obtai
32、n a sample of 8 to 16 g for a briquet about25 mm (1 in.) in diameter or 14 to 20 g for a briquet about 32mm (114 in.) in diameter. If the coal sample has not previouslybeen air dried, air dry this sample at room conditions.7.7 Place portions of the coal sample to be shipped or storedin a container t
33、hat meets the requirements of 5.9.8. 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. A suitableprocedure for use with the epoxy resin described in Note
34、3 isas follows:8.1.1 Add activator or hardener, in the amount recom-mended by the supplier, 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 re
35、sin into thecoal sample. Continue to add resin, a few drops at a time, andstir until 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 ins
36、ert the lower plunger. Fill themold with the coal-resin mixture. Insert the upper plunger,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 appli
37、cation and release of pressure removes airbubbles introduced when the coal is mixed with the resin.8.1.3 Allow the briquet to harden adequately for polishing.Overnight at room temperature or 4 to8hat35to40C issufficient.8.1.4 Eject the coal briquet from the mold using the specialattachment on the pr
38、ess 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 attachment. Use a series ofa
39、brasives 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 shall be free of pit
40、s 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 free of charring and
41、smearing.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. Moisture Control10
42、.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-tance33DeVanney, N., “Impact of Sample Desiccation on the Mean Maximu
43、m 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 Carbide Paper Polishing with Alumina on Fabric SupportPlanNo.Stage
44、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 overcotton cloth.3 240 grit 400 grit . 0.3 m on chemotextile 0.05
45、 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 twolayers of cotton clothD279707310.2 If the vitrinite reflectance is
46、 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 reflectance.NOTE 6During the wet polishing process, some coals absorb moistu
47、rethat 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 mois
48、ture.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
49、all briquets and penetratebelow the surface layer of particles. In subsequent grindingsteps, 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, quartz), can scratch the surfaceor, if soft enough (for example, soot), can smear it.X1.3 Polishing abrasives are usually applied as a slurry indistille
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