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IS 9127-4 (2001): Methods for Petrographic Analysis ofCoal, Part 4: Method of Determining Microlithotype,Carbominerite and Minerite Composition [PCD 7: SolidMineral Fuels]

IS 9127 (Part 4) :2001ISO 7404-4:1988

Indian Standard

METHODS FOR PETROGRAPHICANALYSIS OF COAL

PART 4 METHOD OF DETERMINING MICROLITHOTYPE,

CARBOMINERITE AND MINERITE COMPOSITION

Ics 73.040

0 BIS 2001

BUREAU OF IN DI AN STAN DARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

February 2001 Price Group 3

Solid Mineral Fuels Sectional Committee, PCD 7

NATIONAL FOREWORD

This Indian Standard (Part 4) which is identical with ISO 7404-4:1988 ‘Methods for the petrographicanalysis of bituminous coal and anthracite — Part 4 : Method of determining microlithotype,carbomineriate and minerite composition’ issued by the International Organization forStandardization (ISO) was adopted by Bureau of Indian Standards on the recommendation of SolidMineral Fuels Sectional Committee and approval of the Petroleum, Coal and Related ProductsDivision Council.

The text of ISO Standard has been approved as suitable for publication as Indian Standard withoutdeviations. Certain conventions are, however, not identical to those used in Indian Standards.Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should beread as ‘Indian Standard’,

b) Comma (,) has been used as a decimal marker while in Indian Standards, the currentpractice is to use a full point (.) as the decimal marker.

In this adopted standard, reference appears to certain International Standards for which IndianStandards also exist. The corresponding Indian Standards which are to be substituted in their placeare listed below along with their degree of equivalence for the editions indicated. However, thatInternational Standard cross-referred in this adopted ISO standard which has subsequently beenrevised, position in respect of latest ISO standard has been given:

internationalStandard

ISO 7404-4:1994 Methods forthe petrographic analysis ofbituminous coal andanthracite — Parl 1: Glossaryof terms

ISO 7404-2:1985 Methods forthe petrographic analysis ofbituminous coal andanthracite — Part 2: Method ofpreparing coal samples

ISO 7404-3:1994 Methods forthe petrographic analysis ofbituminous coal andanthracite — Part 3: Method ofdetermining maceral groupcomposition

ISO 7404-5:1994 Methods forthe petrographic analysis ofbituminous coal andanthracite — Part 5: Method ofdetermining microscopicallythe reflectance of vitrinite

CorrespondingIndian Standard

IS 9127 (Part 1) :1992 Methods ofpetrographic analysis of coal:Part 1 Definition of terms relating topetrographic analysis of coal (firstrevision)

IS 9127 (Part 2) :1979 Methods ofpetrographic analysis of coal:Part 2 Preparation of coal samplefor petrographic analysis

IS 9127 (Part 3) :1992 Methods ofpetrographic analysis of coal:Part 3 Determination of maceralgroup composition of bituminouscoal and anthracite

IS 9127 (Part 5) :1986 Methods ofpetrographic analysis of coal:Part 5 Microscopical determinationof the reflectance of vitrinite

Degree ofEquivalence

Technicallyequivalentwith minordeviations

Technically equivalent withminor deviations. How-ever,this Indian Standard is beingrevised to align with ISO7404-2 : 1985 under dualnumbering system

Technically equivalent withminor deviations. However,this Indian Standard is beingrevised to align with ISO7404-3 : 1994 under dualnumbering system

Technically equivalent withminor deviations. However,this Indian Standard is beingrevised to align with 1S07404-5 : 1994 under dualnumbering system

In this adopted standard the term ‘minerite’ indicates that the mineral matter (for example, clay,quartz, etc) exceeds 60 percent or pyrite exceeds 20 percent by volume.

In reporting the results of a test or analysis made in accordance with this standard, if the final value,observed or calculated, is to be rounded off, it shall be done in accordance with IS 2:1960 ‘Rules forrounding off numerical values (revised)’.

IS 9127 ( Part 4 ) :2001ISO 7404-4:1988

Indian Standard

METHODS FOR PETROGRAPHICANALYSIS OF COAL

PART 4 METHOD OF DETERMINING MICROLITHOTYPE,CARBOMINERITE AND MINERITE COMPOSITION

O Introduction

0.1 Petrographic analyses have been recognized inter-nationally as important in the context of the genesis, verticaland lateral variation, continuity, metamorphism and usage ofcoal. The International Committee for Coal Petrology (ICCP)has made recommendations concerning nomenclature andanalytical methods and has published an extensive handbookdescribing in detail the characteristics of a wide range of coals.The text of this International Standard agrees substantially withthe text of the handbook and incorporates many useful com-ments made by members of the I(XP and by member bodies of1S0/ TC 27, Solid mineral fuels.

Petrographic analyses of a single coal provide infortnationabout the rank, the maceral and microlithotype compositionsand the distribution of mineral matter in the coal. The reflec-tance of vitrinite is a useful measure of coal rank and thedistribution of the reflectance of vitrinite in “a coal blend,together with a maceral group analysis, can provide informa-tion about some important chemical and technological proper-ties of the blend.

This International Standard is concerned with the methods ofpetrographic analysis currently employed in characterizingbituminous coal and anthracite in the context of theirtechnological use. It establishes a system for petrographicanalysis and comprises five parts, as follows:

Part 1: Glossary of terms.

Part 2: Method of preparing coal samples.

Part 3: Method of determining maceral group composition.

Part 4: Method of determining microlithotype, carbo-minerite and minerite composition.

Part 5: Method of determining microscopically the reflec-tance of vitrinite.

For information on the nomenclature and analysis of browncoals and Iignites, reference should be made to the /inte-

rnational Handbook of Coal Petrography published bythe ICCPI).

0.2 Microlithotypes are the naturally occurring associationsof macerals which characterize the visibly different types ofcoal. By convention, the identity of a microlithot ype is deter-mined by the maceral group or groups occurring within an areaof at least 50 ~m x 50 ~m and which are present in amountsequal to or exceeding 5 ’10 by volume. Hence they can com-prise a single maceral or maceral group if it exceeds thesedimensions. Microlithotypes may include up to 20 ‘%. byvolume of minerals such as clay, quartz and carbonates or up to5076 by volume of sulfide minerals. If the content of mineralmatter exceeds these amounts, the material is designated asminerite or carbominerite depending on the proportions of coaland mineral matter.

Carbominerites can be subdivided according to the type o;mineral matter.

Microlithotypes contribute information on the genesis of coalseams and can assist in solving problems of seam correlation.Because they determine, together with rank and mineral mat-ter, the hardness and density of the bulk coal substance,microlithotypes affect the behaviour of coal in mining and coalpreparation processes, The different microtithotypes deter-mine, under given geological conditions, the distribution ofmicro-cracks and to some extent the cleat in the coal. Theresults of maceral analyses can be interpreted more mean-ingful y from a knowledge of microlithotype composition. Suchinformation can assist in explaining the behaviour of coal incommercial and experimental utilization processes where dieassociation of macerals is known to be important.

1) The second edition (1963), together with the supplement issued in 1971, maybe obtained from Professor D.G. Murchison, Organic Geochemist~Unit, Department of Geology, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU, United Kingdom. The supplement issued in 1973 may beobtained from Centre National de la Recherche Scientifique, 15 quai Anatole-France, F-750D7 Paris, France.

1

IS 9127 ( Part 4 ) :2001ISO 7404-4:1988

NOTE – The percentage volume of carbonate, clay and quartzminerals on the one hand and sulfide minerals on the other, whichdefine the carbominerites and minerites, correspond to the densitieswhich separate coal from middlings and middlings from discard in coalpreparation.

1 Scope and field of application

This part of ISO 7404 specifies a method, using a graticuie with20 crossline intersections, for determining the proportions ofmicrolithotypes, carbominerite and minerite in coals. It appliesonly to determinations made on polished particulate blocksusing reflected white light.

2 References

ISO 7404, Methods for the petrographic analysis of bituminous

coal and anthracite

– Part 1: Glossary of terms.

– Part 2: Method of preparing coal samples.

— Part 3: Method of determining maceral group compo-

sition.

— Part 5: Method of determining microscopically the

reflectance of vitrinite.

3 Definitions

For the purposes of this part of ISO 7404, the definitions ofISO 7404-1, together with the following, apply.

point: An observation of a portion of the particulate blockthrough the eyepiece graticule made during the analysis.

NOTE – The allocation of a point to a particular microlithotype, or tocarbominerite or minerite, is determined by the macerals and/ormineral matter present at the 20 intersections of the graticule. A pointis only counted if at least 10 intersections fall on a particle.

4 Principle

Examination by using a reflected light microscope and pointcount procedure of a representative sample of coal prepared asa particulate block as described in ISO 7404-2. Identificationunder an immersion medium of the microlithotypes from theirmaceral composition. The proportions of the macerals aredetermined using a graticule having a grid with 20 points ofintersection spaced .to define a distance of 50 ~m on thespecimen between extreme intersections in the x (abscissa) andy (ordinate) directions respectively. The use of such a graticuleallows the analyst to comply with the 5 YO minimum contentand 50 ~m minimum size stipulation.

5 Material

Immersion medium, having a suitable refractive index andcompatible with the microscope objective.

NOTE – If reflectance measurements are required on the sameparticulate block an immersion oil as specified in ISO 7404-5 should beused.

6 Apparatus

6.1 Reflected light microscope, havingan immersionob-jective of magnification between X 25 and X 60 and eyepiece ofmagnification between X 8 and X 12. The eyepiece shall havethe facility for inserting a graticule.

6.2 Greticule, inscribed with a grid having 20 crosslineintersections according to the pattern shown in figure 1. Theeffective distance between extreme intersections in the x and ydirections respectively is SO Nm.

Ill

wFigure 1 – Design of grid for microlithotype analysis

NOTES

1 With a total number of 20 crossline intersections a maceral appear-ing beneath a single intersection can be assumed to occupy 5 Y. byvolume of the area covered by the grid,

2 The graticule is designed for use with a particular combination ofobjective and eyepiece. Change in either objective or eyepiece willnecessitate the use of a grid of different dimensions.

6.3 Mechanical stege, capableof advancingthe specimenin the x-direction by equal steps of such length that only anegligibly small proportion of the particles examined receivesmore than one count on the same particle. The step-length isequal to half the maximum particle diameter, i.e. 0,5 to 0,6 mmfor samples with a standard top particle size of 1 mm. The stagealso permits a similar stepped advance in the y-direction. Thestage movement may be actuated manually or by the countermechanism.

IS 9127 ( Part4 }: 2001ISO 7404-4:1988

6.4 Counter, capable of registering the points in each

category and preferably the grand total of points counted.

6.5 Sample mounting equipment, comprising slides,modelling CIGYand Ievelling press.

7 Procedure

Insert the graticule (6.2) into the eyepiece of the microscope(6.1).

Adjust the microscope for Kohler illumination. Place thelevelled particulate block, prepared in accordance withISO 7404-2, on the stage. Add the immersion medium to thbsurface of the block, focus and observe the image in themicroscope.

Assess the number of crossline intersections lying on the par-ticle in order to decide whether th6 point should be recorded inthe counting procedure and, if so, whether it should be as-signed to the category of a microlithotype, carbominerite orminerite. If the number of intersections on one particle is 10 ormore the point shall be accepted for analysis. If there are no in-tersections on coal or mineral matter, the point is ignored (i.e. itis not recorded). If the number is less than 10 it shall be re-corded as a rejected category and the stage shall be advancedby one step. The number of such rejected points shall notexceed 10 YO of the total accepted and rejected points. If theproportion exceeds 10 Y., excessive fines may have been pro-duced during preparation and a fresh sample should beprepared if material is available. If this is not possible the factshall be recorded in the test report. For identifying the materialunder the individual crosslines, apply the procedure describedin ISO 7404-3. The criteria for determining accepted and re-jected points are shown in figure 2.

If the particle is accepted for analysis, assess the number ofintersections lying on mineral matter. If the number of crosslineintersections on mineral matter exceeds the number shown intable 1 for a given number of intersections lying within the par-ticle, the material is either carbominerite or minerite,

Table 1 – Maximum permissible number of intersectionsfalling on mineral matter for the point to be classified

as a microlithotype

No. of Number of intersections onintersections csrbonate,lying within clay, sulfidethe particle quartz

16 to 20

I3 0

llto15 2 010 1 0

If the particle is a microlithotype, it is identified according to thecriteria shown in table 2 ignoring any intersections on car-bonate, clay or quartz.

Table 2 – Delimitation of microlithotypes

Microlithotype

Vitrite

Liptite

Inertite

Clarite

Durite

Trimacerite

These criteria arf

Location of the crossline intersectionslying in the coal

All intersections in the vitrinite

All intersections in the exinite (Iiptin:te)

All intersections in the inertinite

All intersections in the vitrinite andexinite, at least one intersection in eachof the two maceral groups

All intersectionsin the inertinite and exinite, at least one intersection in eachof the two maceral groups

All intersections in the vitrinite and inertinite, at least one intersection in eachof the two maceral groups

At least one intersection in each of thethree maceral groups

mplicable to microlithoty~es containirwmineral matter not exceeding the limits given in table 1. “

If the intersections on mineral matter exceed the limits gwen intable 1, determine whether the particle is minerite or a car

bominerite according to the criteria given in table 3 and table 4,if necessary. In using table 3 to identify carbomin.?rite or

Table 3 – Delimitation of carbominerite (excluding carbopoiyminerite with sulfide)and minerite

‘“”of I’__&Gninerite ‘-7-

Intersections falling on specified minerals

intersections Mineritalying within J

Carbonate,particle Sulfide

Carbonate,clay, quartz clay, quartz Sulfide

19 or 20 4 toll lt03 > 11 >3170r18 4 to 10 lt03 ~~10 >3

16 4to 9 lto3 >9 ~ >3

14 or 15 3to 8 10r2 >8 I >2

120r13 3to 7 lor2 >7 I >2

11 3to 6 10r2

11> 6 >2

10 2to 5 >5 I >1

3

IS 9127 ( Part 4 ) :2001ISO 74044:1988

minerite, the minerals appearing under tha intersections shallbe either sulfide or other minerals, but not both. Thecarbominerite may be named csrbankerite, carbargilite, ca”r-bosilicite, csrbopyrhe or cerbopolyrninerite, according to themineral matter appearing under the intersections.

If both sulfide and other minerals occur under intersections ofme grid, within the limits given in table 4, the carbominerite isnamed carbopolyminerite, otherwise the particle is againassigned to minerite.

Table 4 – Delimitation of carbopolymineritewith sulfide

~

Intersectionfalling on specified

16t020 lto3 lto311 to 15 lor2 lor2

10 1 1

The maceral group or groups associated with the mineralmatter and appearing under the residual intersections of thegrid may be recorded to further characterize the carbominerite.

Having identified the point, advance the particulate block byone step along the x-axis, and continue counting and traversingthe specimen. At the end of a traverse, advance the block by astep of at least equal length along the y-axis to start the nextparallel traverse. The step length shall be chosen to ensure auniform counting of points over the surface of the particulateblock.

The total number of accepted points shall be at least WO.

NOTE – For the assignment of a microlithotype, only the maceralgroup or groups appearing under the crossline intersections are con-sidered, If a natural boundary between the two different micro-Iithotypes lies under the grid, the assessment is made as if there wereno boundary.

8 Expression of results

Report the number of accepted points per microlithotype, percarbominerite and per minerite as the percentage of totalnumber of accepted points. Express the values obtained aspercentages by volume to the nearest integer.

The number of accepted points and the percentage of rejectedpoints shall be indicated in the test report. An example of asuitable method of expressing results is shown in table 5.

The nature of coal associated with carbominerite and minerite,if determined, expressed as

a) general qualitative observations; or

b) quantitative record of maceral groups under residualintersections

may be recorded as shown in table 6.

Teble 5 – An example of a method of expressingthe reeults

Sample No. Date:

Microlithotype

VitriteLiptiteInertiteClariteDuriteVitrinertiteTrimacerite

Number of I Volume %scceptedpoints

101 20

64 1357 11

115 23

141 2s

Total microlithotypes 95

Cerbominerite Number of Volume %eccepted points

CarbargiliteCarbankeriteCarbosiliciteCarbopyrite LL_

Total carbominerite 4

Number of Volume “Asccepted points

Minerite 4 1

Grand total 100

Total number of accepted points 500Percentage of rejected points 7

Table 6 – Neture of coal associated with carbomineriteand minerite (example)

AcceptedCarbo- Associatad

Number points asmineritel maceral

of accepteda percentage

minerite group(a)points

of(specify) observedl~ cerbominerite/

minerite

1) E = exiniteI = inertiniteV = vitrinite

9 Precision

9.1 Repeatability

The repeatability of the determination of the volume per-centage of a component is the “difference between two singledeterminations each based on the same number of pointcounts carried out by the same operator on the same sample,using the same apparatus, below which 95 % of such dif-ferences would be expected to lie. The repeatability may becalculated from the formula

(2W) C7,

where at is the theoretical standard deviation.

IS 9127 ( Part 4 ) :2001ISO 7404-4:1988

Provided that the operator makes negligible errors in classifyingthe microlithotypes, the results of an enalysis will be subject tostandard deviations calculable on the basis of the binomialdistribution. Where P % of the total number of counts, N, isregistered for a given microlithotype, the standard deviation,Ut, of p is given try the equation

.t=rValues for the theoretical standard deviation and repeatabilitycalculated for a range of volume percentages of a componentare given in table 7 basad on 500 point counts.

Table 7 – Theoretical standard devietionand repeatability of the percentage of a component

based on 500 point counts,

Volume Standarddeviation, at, Repeatability,

percentage,

Pof the volume (2 J-Z) 0,

parentage

II5 1,0 2,8

20 1,8 5,150 2,2 6,3WI 1,8 5,195 1,0 2,8

9.2 Reproducibility

The reproducibility of the determination of the voluma per-centage of a component is the difference between two single

determinations each based on the same number of pointcounts, carried out by two different operators on two separatesub-samples taken from the same sample, using differentequipment, below which 95 % of such differences would beexpected to lie. The reproducibility is given by the formula

(2@) a.

where U. is the observed standard deviation.

Values of the observed standard deviation normally exceedthose of the theoretical values given in table 7 due to mis-identification of the microlithotypea or minerals by differentoperators and to variation between sub-samples. There is, atpresent, insufficient evidence from collaborative analyses toestimate the effect of misidentification.

10 Test report

The test report shall include the following information:

a) reference to this part of ISO 7404;

b) all datails neceaaa~ for identification of the sample;

c) number of accepted points analysed and the percen-tage of rejected points;

d) the results obtained;

e) the nature of coal associated with the carbomineriteand minarite if determined.

IS 9127 ( Part 4 ) :2001ISO 7404-4:1988

- ~trinitenite

xinite

I Immersion medium

a) point acceptedAll intersectionson coalMicrolithotypevitriteAll intersectionson Vitrinite

b) Point accepted> 10 intersectionson ~oelMicrolithotypaclarite9 intersectionson vitrinite,2 on exinita

c) Point rejected but recorded aaparately< 10 intersections on coal d) NOpoint racorded

NO intareectionson COSI

NOTE – The count of interaectiom is made on a singleparticle.

Figure 2 – Criterie used to determine the catagoriaa of accaptad and rajactad pointa

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This Indian Standard has been developed from Doc : No. PCD 7 (1 169).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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