1、Designation: D 720 91 (Reapproved 2004)e1Standard Test Method forFree-Swelling Index of Coal1This standard is issued under the fixed designation D 720; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTESection 1.2 was editorially inserted in March 2005.1. Scope1.
3、1 This test method2is a small-scale test for obtaininginformation regarding the free-swelling properties of a coal.The results may be used as an indication of the cakingcharacteristic of the coal when burned as a fuel. This test is notrecommended as a method for the determination of expansionof coal
4、s in coke ovens.1.2 WarningBreathing of asbestos dust is hazardous.Asbestos and asbestos products present demonstrated healthrisks for users and for those with whom they come into contact.In addition to other precautions, when working with asbestos-cement products, minimize the dust that results. Fo
5、r informa-tion on the safe use of chrysoltile asbestos, refer to, Safe Useof Chrysotile Asbestos: A Manual on Preventive and ControlMeasures.31.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purpor
6、t 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 Documents2.1 ASTM Standards:4D 201
7、3 Practice of Preparing Coal Samples for Analysis3. Significance and Use3.1 This test method, in addition to indicating the cakingproperties of a coal when burned as a fuel, can be used to givea broad indication of the degree of oxidation of a coal.4. Apparatus4.1 This test method can be made with e
8、ither electric or gasheating. When using electric heating, the results obtained mustbe the same as those obtained when using the gas heatingmethod. The apparatus common to both electric and gasmethods shall consist of the following:4.1.1 Crucible, translucent silica, low-form, with a flat,close-fitt
9、ing silica ring-handle lid and an extra pierced lid foruse in determining the crucible temperature, conforming to thefollowing requirements:Weight, g 11.0 to 12.75External height, mm 26 6 0.5External diameter at top, mm 41 6 0.75Internal diameter at base, min, mm 11Capacity (approximate), cm3174.1.2
10、 Sight Tube, as shown in Fig. 1, for viewing the cokebuttons so that the effect of parallax will be eliminated. Makethe tube of any rigid and preferably opaque material andsupport vertically on a ring stand.4.1.3 Thermocouple and Potentiometer.4.1.4 Weight, 500 g.4.2 The electric apparatus shall con
11、sist of the following:4.2.1 Furnace, consisting of a base, a heating element, anda chimney. The unit is shown in Fig. 2.1This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke and is the direct responsibility of Subcommittee D05.15 on MetallurgicalProperties of Coal and Cok
12、e.Current edition approved April 1, 2004. Published May 2004. Originallyapproved in 1943. Last previous edition approved in 1999 as D 720 91 (1999).2This test method is an adaptation of the Crucible Swelling Test for Coal of theBritish Standards Institution. For information concerning the experiment
13、al work onwhich this adaptation is based, see paper by Ostborg, H. N., Limbacker, H. R., andSherman, R. A., “An Experimental Investigation of the British Standard Method forthe Crucible Swelling Test for Coal,” Proceedings, Am. Soc. Testing Mats., Vol 42,1042, p. 851. See also a paper by Selvig, W.
14、A., and Ode, W. H., “An Investigationof a Laboratory Test for Determination of the Free-Swelling Index of Coal,” U.S.Bureau of Mines Report of Investigation 4238, Revision of R. I. 3989, 1948.3Chrysotile Institute 1200, McGill College Suite 1640 Montreal, Quebec CanadaH3B 4G74For referenced ASTM sta
15、ndards, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
16、 PA 19428-2959, United States.4.2.1.1 ChimneyFig. 2 shows the chimney design. Makethe unit from firebrick and coat with firebrick bonding mortar.Maintain the chimney under compression by a sheet-metalenvelope (Fig. 2) to prevent cracking. Make the envelope infour pieces, each piece covering a corner
17、. The pieces shalloverlap at the center of the flat faces and be held together bybolts and springs. Place two layers of asbestos paper betweenthe chimney brick and the envelope. Cut two grooves in theupper inside chimney walls to accommodate the cruciblesupport. In cases in which the furnace is loca
18、ted in a draftyarea, it is advisable to shield the chimney to prevent largefluctuations in furnace temperature.4.2.2 Crucible SupportA convenient crucible supportconsists of a cradle support made from nickel-chromium wiresuspended from a metal ring. The height of the support insidethe furnace can be
19、 adjusted by loosening the two screws thathold the wire legs of the support in place.4.2.3 Electric Controls, consisting of a rheostat, an a-cammeter, and two timers. These components shall conform tothe following specifications:Ammeter a-c, 0 to 10-A rangeRheostat 100 W, 10 VVariable transformer 7.
20、4 A, 120 VTimer mechanical, 05 min minimum span, with a holdposition, and electrical contact closed duringtiming cycle4.2.3.1 One timer shall actuate the rheostat, at a predeter-mined setting, after 112 min of operation. Preset the rheostat toreduce the rate of heating of the furnace so that a tempe
21、ratureof 820 6 5C (1508 6 9F) is achieved at the end of 212 min.A variable transformer is desirable for establishing the inputvoltage to the furnace.4.3 The gas apparatus shall consist of the following:4.3.1 Burner AssemblyA gas burner with a grid of exter-nal diameter, 30 to 42 mm (1.18 to 1.65 in.
22、), a draft shield, anda triangular crucible support as shown in Fig. 3. Make the draftshield, conforming to the dimensions shown in Fig. 3 from theasbestos-cement pipe, and at the top it shall have three slots, 25mm (1 in.) in depth, in which the wires of the crucible supportrest. Support the draft
23、shield on a ring stand, so that thedistance between the base of the crucible and the top of theburner grid may be adjusted by raising or lowering the draftshield. Make the triangular crucible support from three piecesof translucent silica tubing each 63 mm (2.5 in.) in length, 6 to6.5 mm (0.24 to 0.
24、26 in.) in external diameter, and mounted onchromium-nickel wire so that the diameter of the inscribedcircle is approximately 32 mm (1.26 in.). The twisted ends ofthe triangle may be joined together by a loop of wire tofacilitate removal of the hot crucible.4.3.2 FlowmeterA capillary flowmeter with
25、water ma-nometer placed in the gas line before the burner as a guide tothe control of the rate of gas flow (Fig. 3).5. Calibration5.1 Electric Furnace:5.1.1 Turn the main power switch on and set the timer to theHOLD position. Adjust the variable transformer so that theammeter reads 5.8 A. Allow at l
26、east 45 min for the furnacetemperature to reach equilibrium.5.1.2 Set the timer just beyond the 112-min mark. At 112min, lower an empty crucible with pierced lid into the furnace.Measure the temperature at the inside base of the crucible witha thermocouple and a potentiometer. The unprotected juncti
27、onof the thermocouple must be in contact with the inside base ofthe crucible.At the end of 112 min, the temperature should read800 6 10C (1472 6 18F). Adjust the variable transformer asnecessary to provide this temperature.5.1.3 A temperature of 820 6 5C (1508 6 9F) must beattained at the end of 212
28、 min. The second timer shall be usedhere. The control unit rheostat must be properly adjusted toreduce the heating rate at the end of 212 min. If the rheostat isset initially so that at the end of 112 min the ammeter readingis reduced by 0.6 or 0.7 A, the specified temperature at the endof 212 min s
29、hould be attained. Several trials will no doubt benecessary before the proper temperatures at 112 and 212 minare reached; however, the information given above provides ageneral guide for calibration. The silica crucible and covermust be at room temperature before each calibration run.5.1.4 After eac
30、h calibration attempt or sample run, switchthe timer to the HOLD position, and allow about 1 min for thefurnace to reach equilibrium.5.2 Gas Burner:5.2.1 With the burner assembly arranged as shown in Fig. 3,and with an empty crucible in position, light the burner about15 min before making a determin
31、ation to allow the draft shieldto rise to an equilibrium temperature.5.2.2 After placing a crucible in position adjust the flow ofgas and the relative positions of the burner and the draft shieldso that the temperature of the inner surface of the bottom of thecrucible reaches 800 6 10C (1472 6 18F)
32、in 112 min and820 6 5C (1508 6 9F) in 212 min. These desired tempera-tures may usually be obtained by setting the draft shield so thatthe bottom of the crucible is approximately 10 mm (0.4 in.)above the burner grid, and then adjusting the gas flame.Determine the crucible temperature by means of a th
33、ermo-couple and a potentiometer. Insert the thermocouple throughthe pierced crucible lid so that the unprotected junction of thethermocouple is in contact with the base of the crucible.FIG. 1 Sight TubeD 720 91 (2004)e126. Preparation of Sample6.1 Grind the sample of coal to pass a 250-m (No. 60)sie
34、ve and prepare it in accordance with the requirements ofPractice D 2013.6.1.1 The test should be performed within 24 h of the timethat a sample is pulverized to 60 mesh.NOTE 1For some coals, size consist of the sample is a variable thatcan affect the size of the coke button produced.7. Procedure7.1
35、Preparation of Coke Buttons:7.1.1 Electric MethodWeigh1goftheprepared sampleinto a cold crucible and level by lightly tapping the crucibletwelve times on a solid surface, rotating it between taps. Coverthe crucible with a solid lid. Set the control-unit timer just pastthe 112-min mark and set a sepa
36、rate timer at the 212-min mark.As the control-unit timer passes the 112-min mark, lower thecrucible into the furnace and at the same time start the 212-mintimer. The rheostat will be actuated at the end of 112 min. Therun will be finished at the end of 212 min. Remove the cokebutton carefully and re
37、move the carbon residue remaining inthe crucible by ignition. Make three buttons in this manner foreach sample of coal tested.7.1.2 Gas MethodWeigh1goftheprepared sample intoa cold crucible, and level by lightly tapping the crucible twelvetimes on a solid surface, rotating it between taps. Cover the
38、crucible with a solid lid and place it upright in the silicatriangle supported in the draft shield, directly over the gasflame. Heat the covered crucible in the gas flame for the timerequired for the flame of the burning volatile matter to die out,but in any case for not less than 212 min. Remove th
39、e cokebutton carefully and remove the carbon residue remaining inthe crucible by ignition. Make three buttons in this manner foreach sample of coal tested.7.2 Measurement of Coke Button:7.2.1 View each coke button through the sight tube andcompare it with the series of standard profiles shown in Fig
40、. 4.Place the standard profile with which a button is to becompared exactly in the center of the field of vision as viewedFIG. 2 Furnace Base and ChimneyFIG. 3 Details of Burner AssemblyD 720 91 (2004)e13from the top of the tube. Place the button on the profile androtate it on its axis until, viewed
41、 with the eye placed immedi-ately over the top of the tube, the maximum cross-sectionalarea is obtained. Record the number of the standard profilemost nearly matched by the maximum cross-sectional area ofthe button as the swelling index. If any button deviates by morethan one unit from the other two
42、 buttons, make a newdetermination.7.2.2 Some coals give buttons that do not conform in shapeto the standard profiles. For such coals, measure the maximumcross-sectional areas of the buttons and determine the indexfrom the relationship of the areas of the standard profiles toswelling indexes as shown
43、 in Fig. 5. For measuring thecross-sectional areas, mount the buttons on graph paper ruledinto square centimetres and square millimetres, and trace theoutlines of the buttons on the paper while viewing through thesight tube shown in Fig. 1. The buttons may be mountedconveniently by means of modeling
44、 clay. The squares insidethe outline may be counted, and fractions of squares along theboundary line estimated.FIG. 4 Full-Scale Standard Profiles and Corresponding Index NumbersFIG. 5 Relationship of Areas of Standard Profiles to Swelling IndexesD 720 91 (2004)e14NOTE 2To take care of buttons whose
45、 cross-sectional area is greaterthan that of standard profile 9, the curve shown in Fig. 5 has been extendedto include about 700 mm2(1.08 in.2) which is the maximum cross-sectional area of the silica crucibles used in the test.7.2.3 Mechanical or electronic devices may be used todetermine the standa
46、rd profiles if they give results equivalent tothose obtained with measurement techniques described in 7.2.1and 7.2.2.7.2.4 If the residue is coherent but nonswollen, place it on aflat surface and carefully place a 500-g weight on the button. Ifthe button disintegrates, report the swelling index as o
47、ne half.If the button supports the weight or merely cracks into two orthree hard coherent pieces, report the number as one.8. Report8.1 Report the average swelling index of a series of threebuttons expressed to the nearest one-half unit. If this testmethod is to be used for International Classificat
48、ion of hardcoal by type, make five buttons. Report the swelling index aszero if the residue from the test sample is noncoherent.9. Precision and Bias59.1 PrecisionThe relative precision of this test method forthe determination of free-swelling index covers the index rangefrom one to nine.NOTE 3A tes
49、t result is considered to be an average of three FSIdeterminations.9.1.1 RepeatabilityThe difference in absolute value be-tween two consecutive tests results, carried out on the samesample in the same laboratory by the same operator using thesame apparatus, should not exceed the repeatability intervalI(r) more than 5 % of such paired values (95 % confidencelevel). When such a difference is found to exceed the repeat-ability interval, there is reason to question one or more of thetest results. The repeatability interval for this test me
