1、Ref. No. DIN 51742 : 2001-07English price group 06 Sales No. 010605.02DEUTSCHE NORM July 200151742Continued on pages 2 to 6. No part of this translation may be reproduced without the prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the
2、exclusive right of sale for German Standards (DIN-Normen).Determination of the Hardgrove grindabilityindex of hard coalTranslation by DIN-Sprachendienst.In case of doubt, the German-language original should be consulted as the authoritative text.ICS 75.160.10Prfung fester Brennstoffe Bestimmung der
3、Mahlbarkeit vonSteinkohle nach HardgroveIn keeping with current practice in standards published by the International Organization for Standardization(ISO), a comma has been used throughout as the decimal marker.General tolerances shall be class c tolerances as in ISO 2768-1.ForewordThis standard has
4、 been prepared by Technical Committee Prfung fester Brennstoffe of the Normenaus-schuss Materialprfung (Materials Testing Standards Committee). It comforms in substance to InternationalStandard ISO 5074, from which it differs in that use of an air-jet sieve is permitted.AmendmentsThis standard diffe
5、rs from the August 1989 edition in that a reproducibility limit has been included and it hasbeen brought into line with current standards practice.Previous editionDIN 51742: 1989-08.All dimensions are in millimetres.1 ScopeThis standard specifies a method of determining the Hardgrove grindability in
6、dex of hard coal, which is usedin designing and operating coal pulverizers in power stations, cement works and elsewhere.2 Normative referencesThis standard incorporates, by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places
7、in the text, and the titles of the publications arelisted below. For dated references, subsequent amendments to or revisions of any of these publicationsapply to this standard only when incorporated in it by amendment or revision. For undated references, thelatest edition of the publication referred
8、 to applies (including amendments).DIN 51701-2 Sampling of solid fuels ProcedureDIN 51701-3 Sampling of solid fuels Sample preparationSupersedes August 1989edition.Page 2DIN 51742 : 2001-07Supplement 1 toDIN 51701-4 Sampling of solid fuels Sampling equipmentDIN 51718 Determining the water content an
9、d analytical moisture content of solid fuelsDIN EN ISO 4259 Petroleum products Determination and application of precision data in relation to meth-ods of test (ISO 4259 : 1992 + Corr 1 : 1993)DIN ISO 3310-1 Test screens Technical requirements and testing Part 1: Test sieves of metal wire cloth(ISO 3
10、310-1 : 1990)ISO 2768-1 : 1989 General tolerances Part 1: Tolerances for linear and angular dimensions without indi-vidual tolerance indicationISO 5074 : 1994 Hard coal Determination of Hardgrove grindability index3 PrincipleA coal sample of a defined particle size range is ground under specified co
11、nditions in a laboratory Hardgrovemachine. The grindability index is determined by comparing the results of a sieve analysis of the ground samplewith a calibration graph plotted using standard reference material.4 ApparatusThe following equipment shall be used.a) Balance, capable of weighing up to 1
12、00 g to an accuracy of 0,01 g.b) Balance, capable of weighing up to 1500 g to an accuracy of 1 g.c) Sample divider, as specified in subclause 2.2 of Supplement 1 to DIN 51701-4, August 1985 edition.d) Crusher (e.g. hand mortar, laboratory jaw crusher or disc mill), capable of reducing the particle s
13、ize ofcoal from less than 5 mm to less than 1,2 mm with the production of a minimum of material finer than 0,6 mm.e) Test sieves, fitted with ISO 3310-1 wire-cloth sieving media, having a cover and a receiver.f) Protective sieve, having round or square apertures in the range 16 mm to 19 mm, capable
14、of beingnested in the test sieves.NOTE: If a test sieve cloth is used as protective sieve, it may be damaged, thereby making it unusable asa test sieve.g) Sieving machine, capable of accommodating vertically nested sieves having a cover and a receiverabout 200 mm in diameter, or an air-jet sieve.h)
15、Hardgrove grindability machine (see figures 1 and 2), comprising a stationary, hardened-steel grindingbowl having a horizontal track containing eight steel balls, each 25,4 mm in diameter and driven by an uppergrinding ring at 19 min1to 21 min1. The upper grinding ring shall be of the same material
16、as the grindingbowl and shall be connected to a spindle driven by an electric motor through reduction gears. The total massof upper grinding ring, spindle, gears and additional loading weights acting on the steel balls shall beequivalent to a force of (284 2) N. The machine shall have a revolution c
17、ounter and an automatic devicefor stopping it after (60 0,25) revolutions. It shall be calibrated by the method described in clause 6 andin Appendix A.5 Sampling and sample preparationCollect and prepare samples as specified in DIN 51701-2 and DIN 51701-3. Take a subsample of at least 2 kgfrom the g
18、ross sample (see table 1 in DIN 51701-3), gently grind it to a particle size of less than 5 mm and, ifnecessary, reduce it to a sample mass of about 2 kg (final sample).Page 3DIN 51742 : 2001-07Figure 1: Hardgrove machineAfter drying the sample material in air (as specified in DIN 51718), weigh the
19、dried sample to an accuracy of 1 g.NOTE 1: It may be necessary to dry all the sample material in air before reducing it to a particle size of less than5 mm.Prepare the test sample from the air-dried material by extracting the 1,18 mm to 0,6 mm fraction (test fraction)by sieving and, to maximize the
20、proportion of ground material in the 1,18 mm to 0,6 mm fraction, reduce theoversize and add it to the test sample. Always discard the fraction below 0,6 mm.It is also permissible to use ISO 3310-1 sieves having similar dimensions (e.g. 1,25 mm and 0,63 mm), butsieves having the same dimensions shall
21、 always be used for calibration and for testing.Direction of rotationRevolution counterPage 4DIN 51742 : 2001-07Figure 2: Grinding elements (sectional view)After carefully mixing the test sample, remove about 120 g of sample material using a sample divider and sievethis quantity for five minutes usi
22、ng the 0,6 mm sieve to remove the fines. Not less than 50 g of the residue soobtained shall be removed with the sample divider.NOTE 2: Samples of certain types of mixed coal may contain agglomerates of fines greater than 0,6 mm thatdo not disintegrate during the dry sieving. In such cases, the fines
23、 shall be removed by wet sieving and thetest fraction then dried in air.6 ProcedureCarefully clean the Hardgrove machine and distribute the steel balls as evenly as possible in the grinding bowl.Weigh a test portion of 50 g of the sample material with the fines removed to an accuracy of 0,01 g and d
24、istributethis quantity uniformly in the grinding bowl, smoothing out the surface. After mounting the upper grinding ring,fit the bowl in the machine and connect the ring to the drive spindle at the same time. Then set the counter andthe automatic stopping device to (60 t 0,25) revolutions and switch
25、 on the machine. When the machine stopson reaching the set number of revolutions, remove the upper grinding ring and brush any adhering coal dustoff onto the protective sieve nested on the 0,075 mm sieve with receiver. Next, empty the ground coal togetherwith the steel balls onto the protective siev
26、e and remove any adhering coal with a brush from the grinding bowland the steel balls. Assemble the grinding bowl, steel balls and upper grinding ring after cleaning.Finally remove coal and coal dust from the inside and bottom of the protective sieve and transfer the resultantmaterial to the 0,075 m
27、m sieve.Place the cover on the 0,075 mm sieve and shake the cover, 0,075 mm sieve and receiver assembly for tenminutes on the sieving machine. Then invert the sieve on a collector and transfer the adhering coal to the latterby carefully brushing along the warp and weft of the cloth. Return the clean
28、ed sieve to the sieve assembly, addthe material in the collector and sieve for a further five minutes. Repeat this operation once more.Finally, clean the sieve so that the residue on the sieve (oversize) and the coal in the apertures enter the collector,while the undersize is collected in the receiv
29、er.Weigh the oversize and the undersize to an accuracy of 0,01 g.NOTE: If the sum of these final masses differs by more than 0,5 g from the mass of sample taken, discard theresult and repeat the determination.The fraction below 0,075 mm can be determined with an air-jet sieve as the difference betwe
30、en the initial massand the oversize.The same sieving method shall be used for calibration and for testing.Page 5DIN 51742 : 2001-077 EvaluationCalculate the mass of the undersize, m, in g, using equation (1):m = m0 m1(1)wherem0is the initial sample mass, in g;m1is the mass of oversize, in g.Determin
31、e the grindability index from the mass of the undersize using the calibration graph (see Appendix A).Report the mean of two determinations carried out on aliquots of the test sample as the Hardgrove grindabilityindex, HGI, after rounding to the nearest integer.8 Precision(cf. DIN EN ISO 4259)8.1 Rep
32、eatability limit(same operator, same equipment)If two results are obtained under repeatability conditions, both results shall be considered acceptable and inconformity with this standard if they differ by no more than the value in column 1 of table 1.8.2 Reproducibility limit(different operators, di
33、fferent equipment)If two separate laboratories each obtain a result under reproducibility conditions, both results shall be consid-ered acceptable and in conformity with this standard if the means of the two results differ by no more than thevalue in column 2 of table 1.Table 1: PrecisionRepeatabili
34、ty limit Reproducibility limitHGI HGI259 Test reportThe test report shall refer to this method and include the following details:a) a discription of the sample material;b) Hardgrove index (with mean and single values, where required).Page 6DIN 51742 : 2001-07Appendix APlotting the calibration graphU
35、se a set of four international or national standard reference coal samples1) having a Hardgrove grindabilityindex of about 40, 60, 80 and 110 to plot the calibration graph. Always prepare and examine each sample induplicate as described in clauses 5 and 6.Plot a graph of the mean mass of material pa
36、ssing through the 0,075 mm sieve (see table A.1) against thegrindability index for each sample and draw a straight line through these four points (see figure A.1). Theevaluation may also be done by calculation.Check the calibration graph every time the machine is repaired or overhauled, or if it is
37、suspected of beingdefective.Figure A.1 shows only one example of a calibration graph. It shall not be used to determine the Hardgrovegrindability index. The test results used to plot the graph were as follows.Table A.1: Calibration dataHardgrove index of standard Mass passing through sieve,reference samples in g40 4,3558 7,1483 10,44107 14,53Figure A.1: Calibration graph (example)1) Standard reference samples are obtainable from the U.S. Department of Energy, PETC, P.O. Box 10940,Pittsburgh, PA 15236, Tel. (412) 492-5898.Mass passing through 0,075 mm sieveHardgrove grindability index, HGI
