COAL SAMPLING PROCEDUREAND ANALYSIS OF COAL

COAL : Non renewable fossil solid fuel formed by a series of natural geochemical process fromthe plant remains accumulated together with other sediments.

COAL SAMPLING & SAMPLE PREPARATIONThe BIS specification No. 1S-436 (Part-I, Section-I) 1964 and IS:436 (Part-II) 1965

describes the method of sampling and sub sampling of the coal/coke so as to achieve arepresentative sample as homogenous as possible for laboratory in 212 micron size.

COAL SAMPLINGIndian standard Institute has laid down some specific sampling procedure which is

obligatory to both the supplier and consumer otherwise both the parties may mutually adoptsome methods on the basis of the ISI specification of sampling.For each consignment of 250 tonne one sample is recommended. After receipt of coal rack inTPS, placement report is filled in which wagon numbers and name of the colliery is mentioned.(2) The standard practice is to collect about 350kg samples for 250 tonnes of coal received

in increments.(3) 25% of total wagons received should be selected from coal sampling Random Table.

R A N D O M T A B L E

8 1 7 4 6 7 9 5 7 0 5 6 5 1 5 4 5 0 5 3

6 1 3 7 4 2 6 2 9 3 9 6 3 4 1 8 2 2 8 9

5 2 0 7 1 6 2 9 3 9 0 4 7 1 1 4 7 6 7 8

4 3 0 8 7 7 2 5 7 2 4 9 8 6 0 3 8 3 4 5

6 5 3 2 2 7 4 0 6 3 5 7 9 7 8 4 8 2 8 7

2 1 5 8 1 1 2 3 8 0 1 0 3 0 0 1 1 0 0 4 4

3 1 9 0 5 5 8 8 1 3 3 6 2 4 9 1 1 9 6 4

7 3 9 8 2 0 0 5 6 8 4 6 6 9 8 5 9 4 5 9

3 3 1 5 3 5 2 6 7 9 9 2 3 8 1 2 4 1 1 7

7 5 6 6 9 9 0 9 0 6 4 7 4 8 6 0 2 8 0 2

(4) About 5 Kg of sample are collected each from four corners and centre from everyselected wagon by digging 0.5 Mtr. Depth.(5) The bulk of 350 Kg sample so collected are well mixed and reduced either by mechanical

sample dividers or by hand methods using shovel by coning and quartering etc.(6) The gross sample is reduced to 50 Kg in stages. The 50 Kg mass is crushed to ?” sizeand again reduced by coming and quartering in stages to get a final sample of about2 Kg. This sample is further reduced by coning and quartering till 1 Kg of sample isobtained.(7) 1 Kg of sample is finally powdered (72 mesh) in Raymond will for analysis.(8) Out of 1 Kg, pulverized fine powdered sample (72 mesh). Two packets of 250 gm

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samples are prepared one is referee sample and other is for analysis.PROXIMATE ANALYSIS :

Proximate analysis which comprises determination of moisture, ash, volatile matter andfixed carbon expressed in terms of weight percentage. This gives quick and valuable informationregarding commercial classification and determination of suitability for a particular Industrialuse.

PROXIMATE ANALYSIS OF COALA) Determination of moisture on air dried basis :-1) Take about 1.5 gms. Of air dried sample in a weighing dish and spread the coal in a

uniformly thin layer.2) Put the weighing dish in hot air oven.3) Heat at temp. of 1080 C + 20 C until there is no further loss in mass. This normally takes

about 1.5 to 3 hrs.4) Express the loss in mass as a % of the total moisture of sample.

100 (M2 - M3)5) M % (Air dried basis) = —————————

(M2 - M1) M1 = Mass in gms. Of empty weighing dish plus lid. M2 = Mass in gms. Of weighing dish with lid plus coal. M3 = Mass in gms. Of weighing dish with lid plus dry coal.

B) Determination of ash on air dried basis :-1) Weigh a clean dry empty crucible and lid.2) Weigh accurately about 1.0 gm. Of laboratory sample and spread the coal uniformly inthe crucible.3) Insert the uncovered crucible into the muffle furnace at room temperature.4) Raise the temp. to 5000 C in 30 minutes and 8150 + 100 C in further 30 to 60 minutes

and maintain at this temp. for 60 minutes. Cover the crucible with lid and remove fromthe muffle furnace and allow to cool for 10 minutes and finally take in a Desicator.

Weigh the mass of ash by difference. 100 (M3 - M1)

5) Ash % = —————————(On Air dried basis) (M2 - M1)

M1 = Mass in gms. of empty weighing crucible plus lid.M2 = Mass in gms. of weighing crucible with lid plus coal.M3 = Mass in gms. of weighing crucible with lid plus Ash.UHV Kcal/Kg = 8900 - 138 (M% + Ash %)

C) % Volatile matter (Vm) :Weigh silica crucible + 1 gm sample with lid heated at 9100 C in furnace for 7 Minutes.Then calculate,% Vm as loss in difference calculated in % - Moisture% = % Volatile matter.

D) Determination of Moisture on Equilibrated Basis :(At 400 C & 600 C R.H.)

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1) Take 4 to 5 gms. coal sample in a clean conical flask/beaker 100 ml. Cap.2) Pour 20 ml D.M. Water.3) Heat this mixture on heating pad/Electrical heater, gently Boil it 10 to 15 minutes.4) Cool the mixture 10 to 15 minutes & filter all the material in next conical flask andpressing the contain in between filter papers.5) Take about 1.5 gms. of wet coal in dish and spread it uniform layer.6) Prepare the H2 SO4 acid having Sp. Gr. 1.280 and transfer it in desiccator. The quantity

of H2 SO4 (Sp. Gr. 1.280) may be 300 ml. to 400 ml. in one desiccator.7) Put the above petridesh without cover in the desiccator.8) Close the desiccator & put this desiccator in a humidity oven at 400 C for 72 hrs.9) Very next day break up the coal lumps & make fine powder & again put in the above

stated oven. Total timing for keeping the desiccator is 72 Hrs. Or till the changein mass does not exceed the 0.001 gms.

E) After 72 Hrs. analyze the moisture percentage by as usual procedure as stated in airdry basis & Calculate into percentage.

NOTE :Only Moisture is actually tested on equilibrated basis. All other air driedvalues are then converted into equilibrated basis, by calculations as follows

:

100 - M2(Eq. M%)Equilibrated Ash % = ————————————— X A% of air dry basis.

100 - M1 (Air dried M%)

100 - M2(Eq. M%)Equilibrated V.M.% = —————————————— X VM% of air dry basis.

100 - M1 (Air dried M%)

Equilibrated F.C.% = 100-[Total of M% + Ash% + VM%]

Equilibrated UHV Kcal/kg = 8900 - 138 (M% + ash%)

COMMERCIAL GRADES OF COAL FOR BILLING CALCULATEDON THE BASIS OF UHV (USEFUL HEAT VALUE)

GRADE UHV (Kcal/Kg)

A

B

C

D

E

F

G

Un / Graded

> = 6200

5601 - 6200

4941 - 5600

4201 – 4940

3361 – 4200

2401 – 3360

1301 – 2400

< 1300

Equilibrated UHV Kcal/kg = 8900 - 138 (M% + Ash %)

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