Plastic Properties of Coal and Their Laboratory Determination

7/27/2019 Plastic Properties of Coal and Their Laboratory Determination

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Assignment

(MEE)

By

Chandan Kumar

110MN0392

Department of Mining Engineering

National Institute of Technology

Rourkela - 769008, India

07 Oct 2013


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Contents

Plastic Properties of Coal and Their Laboratory Determination .................................................... 4Introduction ................................................................................................................................. 4

Caking Index ........................................................................................................................... 4Free Swelling Index ................................................................................................................ 4Gray King Low Temperature Assay (GKLT) ......................................................................... 4

Determination of Caking Index .................................................................................................. 5Outline of the Method ............................................................................................................. 5Apparatus ................................................................................................................................ 5Sand......................................................................................................................................... 6Procedure ................................................................................................................................ 6

Crucible Swelling Number ......................................................................................................... 7General .................................................................................................................................... 7Gas Heating Method ............................................................................................................... 8Electrical Heating Method .................................................................................................... 12

Determination of Low Temperature (LT) Gray-King Assay .................................................... 14General .................................................................................................................................. 14Apparatus .............................................................................................................................. 14Preparation of Coal Sample .................................................................................................. 18

Procedure .............................................................................................................................. 18

Roga Index ................................................................................................................................ 23Gieseler Plastometer Test ......................................................................................................... 23Arnu Dilatometer Test .............................................................................................................. 23RuhrDilatometer ...................................................................................................................... 24

Fighting mine fires using inert gases ............................................................................................ 24Introduction ............................................................................................................................... 24Gas injection systems ................................................................................................................ 25Carbon dioxide .......................................................................................................................... 25Combustion gases ................................................................................................................. 26Nitrogen .................................................................................................................................... 26PSA-based nitrogen generator .................................................................................................. 27


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Membrane based nitrogen gas generator .................................................................................. 29Pumped gas requirements ......................................................................................................... 31The Gag 3A System .................................................................................................................. 32Case Study ................................................................................................................................ 34

Kottadih Colliery .................................................................................................................. 35Sijua Colliery (TISCO) ......................................................................................................... 35GDK - 9 incline, Singareni Collieries ................................................................................... 36Lodna Colliery ...................................................................................................................... 37Laikdih deep colliery (BCCL) .............................................................................................. 37Loveridge Mine ..................................................................................................................... 37Pinnacle Mine ....................................................................................................................... 39

References ..................................................................................................................................... 40


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Plastic Properties of Coal and Their Laboratory

Determination

IntroductionWhen coal is heated, it passes through a transient stage which is called as plastic state (caking).

If a particular coal does not pass through a plastic state, it is called sintered mass(non-

coking).Plastic properties of coal is determined by caking index test, free swelling test, GKLT,

Plastometer etc. Caking, swelling, agglutinating and plastic properties are all interrelated.

Numerous laboratory tests have been proposed for measuring the propensity of these properties.

While some have been developed into standard test, others have become either obsolete or are of

theoretical interests only. The standard tests in vogue in different countries are: Free swelling

index, Gray- King(low temperature) Coke type, Caking (agglutinating) index, Roga index and

Thickness of plastic layer.

Caking Index: It is the measure of binding or agglutinating property of coking coal.

Numerically it is the maximum number ratio of sand to coal in a 25gm mixture of the two (Sand

+ Coal ) which on heating under standard conditions produces a residue coke capable of

supporting a weight of 500gms without producing more than 5% of loose grains of coke. The

Caking Index of coal blend charge for coke ovens is about 21 to 22. If the coal has higher than

17%ash, it has to be washed before testing.

Free Swelling Index: It denotes the caking capacity of coal. In this test 1gm of (-212) coal

samples are taken and heated in a silica crucible of particular dimension. It is heated in a burner

or in a furnace maintained at 825-850C.Heating is carried out for 4 minutes. Maximum value offree swelling index is 9. Coal having free swelling index between 4-5 are taken for coke making.

Gray King Low Temperature Assay (GKLT): It is carried out to observe coking

property of coal.First, 20gm of fine coal of -212 size is taken in a silicon crucible and then the

furnace is pre-heated at 300C. Heating is carried at a rate of 5C/minute till the temperature

reaches 575C, & then increased to 600C quickly. At 600C hold it for 15 minutes. After that

detach the apparatus. The profile inside the crucible is compared with standard coal burden from

A-G, G1, G2.G9, G10.

A - The residue is powder with noswelling

B - Non coking,C & D - weakly caking,E,F & G - medium caking,G1- G9 - High caking.

After heating the sample hard mass obtained = Vol. of the coal sample


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Then it is G. The suffix 1, 2, 3 indicates the no. of grams of inert C required to be added to

the hard mass to give the original profile or standard G-type coke.

Determination of Caking Index

Outline of the MethodFrom a series of tests, the maximum ratio of sand to coal is obtained in a coal sand mixturewhich, after carbonization under specified conditions, gives a coherent mass capable ofsupporting a 500 g mass, at the same time the proportion of loose powder being less than 5percent of the mass of sand and coal. This is the agglutinating index or caking index. It isunderstood that this method provides only an approximate measure of the tendency of a coal toagglutinate or to produce a lump from powder. To ensure reliable comparison, it is necessary thatcomparative tests between different operators should be carried out with supplies from the samebatch of sand. In all cases the batch number should be stated.

Apparatus

Weighing bottle -stoppered, cylindrical, approximately 75 mm in height and 2.5 mm in

diameter.

Sil ica crucible -translucent, with lid, of even taper, the inner surface being free from roughness.

The crucible shall conform to the following dimensions:

Internal diameter at the top of crucible 38 1 mm

External diameter at bottom 26 1 mm

Thickness of walls:At top of crucibleAt bottom

2.25 0.50 mm1.25 to 1.5 mm

Height of crucible 42 0.75 mm

Radius of curvature, rounded edge of cruciblebottom

3.5 mm

Minimum width of lid 46 mm

Maximum width, including extension tofacilitate handling

60 to 62.5 mm

Thickness of lid About 1.5 mm

Diameter of recessed part of lid 36 mm

Depth of recessed part of lid 3 to 4 mm

Spatula -made from sheet metal 0.7 mm (or 22 SWG)

Sili ca tr iangle support - of such dimensions that the crucible is held upright with the base 10

mm above the level of the bench.

Glazed paper


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Muff le fur nace -gas or electrically heated, capable of maintaining a steady temperature of 900

15OC, provided with a closely fitting door. The heat reserve of this furnace should be such that

the temperature is regained before the end of the seven minutes heating period of the test. The

temperature should be determined by means of a suitable insulated thermocouple and

millivoltmeter, the hot junction of the former being placed away from the floor or sides of the

furnace but in the position to be occupied subsequently by the crucible.

Rubber bung -solid, conforming to the following dimensions:

Diameter:

Narrow end 35 mm

Wide end 41 mm

Height 32 mm

Sand

It is extremely important that the sand used in this test should be of uniform quality with regardto size, purity, sharpness, etc. The standard silica sand is not soluble in hot dilute hydrochloric

acid to a greater extent than 0.5 percent. It consists mainly of angular particles of pure silica, and

is free from impurities, such as clay, chalk, or iron carbonate. It is graded to pass IS Sieve 30

(296 microns) and to be retained on IS Sieve 20 (211 microns) containing not more than 5

percent of oversize and not more than 10 percent of undersize, the oversize and undersize

material being not appreciably different from the specified screen sizes. The sand shall not break

down on heating for three hours at 920C to such an extent that the percentage of undersize

material is increased by 2.5. Sand of this quality is obtainable from the Central Fuel Research

Institute F.R.I., Bihar, India.

Procedure

a. Air-dry the coal and grind it so that the material just passes through IS Sieve 20 (211

micron). In preparing the coal to this size, it is essential that very fine grinding should be

avoided since the results obtained are to some extent dependent upon the amount of very

fine material in the sample.

b. Weigh into the weighing bottle, the requisite amounts of the coal and the standard sand to

give 25 g of the mixture, containing the two ingredients in the desired proportions. Mix

the sand and coal by rotating the tube between the finger and thumb, until the mixture is

of uniform appearance to the eye. Pour the mixture into the silica crucible, the innersurface of which having been covered with a layer of graphitic carbon from a previous

test.

c. As some segregation of the ingredients may occur during the transfer to the crucible

complete the mixing by rotating the crucible, resting on its base, with the left hand in a

counter-clockwise direction. At the same time, hold the spatula with the narrower end in

the right hand slightly inclined to the vertical away from the operator with the blade of


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the spatula facing the direction of rotation of the crucible, and with its broader end

immersed in the mixture. Repeatedly raise and lower the spatula while the crucible is

rotated, continue the mixing for two minutes, and withdraw the spatula. Level the surface

of the mixture by pressing gently with the narrower end of the rubber bung, care being

taken during this operation that the crucible is not jarred or the contents tamped.

d. Cover the crucible with its lid and transfer to the silica triangle support. Place the crucible

and the support, in an electric or gas-fired muffle, previously raised to a steady

temperature of 900C 15OC and provided with a closely fitting door. Replace the muffle

door. At the end of seven minutes withdraw the crucible and the support from the furnace

and allow to cool slowly to room temperature while standing on an asbestos board. At the

end of 30 to 40 minutes remove the crucible lid, withdraw the crucible from the support

and place it on its base on a sheet of glazed paper.

e. Place the rubber bung with the narrower end resting on the surface of the contents of the

crucible. Invert the crucible and rubber bung by holding the rim of the crucible and the

rubber bung, on opposite sides, between the thumb and second finger of one hand. Carryout this operation over the sheet of glazed paper so that any particles falling from the

crucible and adhering to the finger and thumb may be collected. Raise the crucible

vertically away from the carbonized residue of sand and coal. Lift the residual cake from

the bung, holding it gently between the finger and thumb (care being taken to product no

powder) and place it with its broad end on a porcelain tile. Gently lower a 500 g mass

until its base rests upon the carbonized residue and not whether the mass is supported

without crumbling. Weigh the loose powder on the glazed paper, together with that from

the top of the bung.

f. After the test, the inner side of the crucible will be found to be covered with a bright layer

of carbon. This should be retained from test to test and should not be burnt off.g. Repeat the test with increasing ratios of sand to coal, the mass of the total mixture always

being 25 g and report as agglutinating index the maximum ratio which supports a mass of

500 g with the proportion of loose powder being less than 5 percent of the mass of the

mixture.

Crucible Swelling Number

General

The swelling number of coal, as determined by the crucible swelling number test, described

below, is intended solely to give some comparative measure of the swelling properties of coals.

From a consideration of the average error, it has been ascertained that the mean result of four

tests on the same coal sample is correct to within 1 unit in 99 out of 100 cases and within 0.5

unit in 80 out of 100 cases, there is thus some assurance that different investigators can closely

reproduce results on the same coal. The source of heat used in the test is a gas burner or

electrically heated furnace. The International Organization for Standardization (ISO) has

recommended both the heating methods.


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Gas Heating Method

Apparatus

APPARATUS FOR CRUCIBLE SWELLING NUMBER TEST

It consists of the following components:-

Si lica

Translucent, squat shape, having a silica lid with ring handle weighing not more than 12.75 g or

less than 11 g with capacity approximately 17 ml and with the dimensions given in Figure.


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CRUCIBLE AND LID FOR CRUCIBLE SWELLING NUMBER

In case where the lower surface of the crucible lid is not flat, difficulty may be experienced in

assessing the swelling number of the coal. To overcome this, it is suggested that a small mica

plate should be inserted between the lid and the crucible before heating the coal.

Si lica tr iangle

Consisting of translucent silica tubing, 6 to 6.5 mm external diameter, mounted on chrome-nickel

wire the length of the side being 63 to 64 mm, the diameter of the inscribed circle being

approximately 32 mm.

Teclu burner

12.7 mm bore. Any other suitable type of burner may also be used.

Draught shield

Made from asbestos cement piping, approximately 150 mm long with 100 mm internal and 110mm external diameters. The piping has three slots at one end, 25 mm deep, in which the wire

portions of the silica triangle rest.

Conditions of Heating

The gas pressure and the gas and air supplies for the burner shall be adjusted by enlarging the

size of the gas jet so that the flame is approximately 300 mm long. With the burner so adjusted,

the position of the crucible, resting in the silica triangle and supported in the draught shield, shall

be so arranged that the flame envelops the crucible and the temperature of the inner surface of

the bottom of the crucible reaches 800C 10C in 1.5 minutes and 820OC 5OC in 2.5 minutes

from the time the gas is ignited first. With these conditions, it will generally be found that the

base of the crucible is just above the tip of the blue cone. These conditions apply particularly to

coal gas of about 4500 KCal/nm3. For gas of much higher or much lower calorific value a

different length of flame may be required. The use of four crucibles so that the test can be carried

out in rapid sequence, following a blank test to warm the draught shield, is helpful when

difficulty is found in attaining the standard rate of heating. These conditions of heating shall be

checked at frequent intervals by means of a fine wire thermocouple inserted through a pierced


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lid, and having its unprotected junction in contact with the center of the base of the empty

crucible. This couple should be made of wires not heavier than 0.22 mm platinum or 0.45 mm

base metal, and the end of the couple should be in the form of flattened loop so that the junction

and a portion of each wire rest on the bottom of the crucible during a temperature measurement.

The conditions for attaining the correct heating having been ascertained, the apparatus may

conveniently remain permanently erected by fixing the draught shield on a suitable support, the

burner remaining centered and being adjusted in situ.

Grinding the Coal

Air-dry the coal to be tested and grind it so that it passes IS Sieve 20 (211 microns).The grinding

should be done not more than two hours before testing coal of weak swelling characteristics to

prevent error due to oxidation.

Procedure

Weigh 1.00 to 1.01 g of the freshly ground coal into a crucible and lightly tap the crucible 12

times on the bench to level the surface of the coal. Cover the crucible with the lid and place it

upright in the silica triangle supported in the draught shield. Light the gas and heat for such time

as is required for the flame of the burning volatile matter to die out, and in any case for not less

than 2.5 minutes. Allow the crucible to cool and carefully remove the coke button. Repeat the

test until four buttons have been obtained. In some cases it may be necessary to prepare 5

buttons. After each test remove the carbon residue in the crucible and wipe the interior of the

crucible clean.

Examination

Compare the coke button with the standard numbered outlines in Figure. For the comparison,

rotate the button about its axis so that the largest profile is presented to view. A method of

viewing which excludes the effect of parallax is shown in Figure. Place-the drawing with which

the button is to be compared exactly in the center of the field of vision from the top of the tube.

Arrange the button so that the maximum cross section is in line with the drawing when viewed

with one eye placed immediately over the top of the tube.

Report

The swelling index of a button is the number inscribed in the outline that its largest profile most

nearly matches. Report the mean swelling number of the series, expressed to the nearest half

number. For non-swollen button, the number 0 is used to describe coals which give a powderresidue. The number 1/2 describes coals which give a coherent residue that will not bear a 500

g mass. The number 1 describes coals which give a coherent residue that cracks into two or

three hard piece when the 500 g mass is applied.


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STANDARD PROFILES AND CORRESPONDING CRUCIBLE SWELLING NUMBERS

APPARATUS FOR VIEWING THE BUTTON


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Thermocouples

Of fine wire of diameter not greater than 0.5 mm if made of chromel alumel. The ends of the

couple shall be in the form of a flattened loop.

DETAILS OF SWELLING INDEX FURNACE

Preparation of Apparatus

Switch on the furnace and adjust the energy input so that a steady temperature of about 850 OC is

maintained at the base of the crucible resting on the silica plate. Remove the crucible and insert a

cold crucible covered with a pierced lid through which passes the fine wire thermocouple held so

that its unprotected junction and a portion of each wire rests on the base of crucible. Ascertain

that the standard heating conditions of 800 10C in 1.5 minute and 820 5 OC in 2.5 minute are

attained from the time of inserting the crucible. If these conditions are not attained, adjust the

furnace temperature until the specified conditions are attained. Record the furnace temperature as

indicated by the thermocouple at the underside of the silica dish, this temperature serving as a

datum.

Procedure

Weigh 1.00 to 1.01 g of the freshly ground sample into a dry crucible and lightly tap the crucible

about 12 times on the bench to level the surface of the coal. Cover the crucible with the

unpierced lid and place it centrally in the furnace on the silica dish. Heat until the volatile matter

ceases to be evolved and in any case for at least 2.5 min. Remove the crucible from the furnace


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and allow it to cool. Examine the residue as specified in Gas Heating Method. Carry out five

tests in succession, replacing one crucible with the next to avoid heat losses through the top of

the furnace. After each test burn off the carbon residue and wipe the crucible with a clean cloth.

Report

Report the swelling number of the coal as specified inGas Heating Method.

Determination of Low Temperature (LT) Gray-King Assay

General

The purpose of the test is to assess the caking properties of a coal or a blend of coals and also the

yield of various byproducts by carbonising in a laboratory under standard conditions at a

maximum temperature of 600OC. The coke residue from the carbonization of finely ground coal

at 600C is classified by comparison with a series of described coke types. For strongly swelling

coals, the coal is blended with electrode carbon or high temperature coke breeze in a proportion

which gives on carbonization, a strong, hard coke of the same volume as the original coal and

electrode carbon/coke breeze mixture.

Apparatus

LOW TEMPERATURE GRAY-KING ASSAY APPARATUS


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Furnace

Ais a 300 mm long tubular electrically heated type capable of giving a uniformly heated space

(within 10C any temperature between 300

O

C and 600

O

C) in the middle 20 cm portion. Thewheels fitted to the furnace facilitate its easy movement over the retort (B). The energy regulator

of the furnace should be capable of allowing temperature rise at the rate of 5OC per minute. The

well fitting ends of insulated material provided prevent undue cooling of the retort by circulation

of air.

Thermocouple

A thermocouple is fitted into a refractory or stainless steel sheeth passing through the rear end of

the furnace and positioned so that the tip of the thermocouple is midway along the length of the

charge and the sheath is almost in contact with the retort when the latter is in the furnace. The

thermocouple is connected with an instrument for measuring the emf or equivalent temperature

difference, the combination being sensitive to 5OC.

Retort

Preferably of transparent borosilicate glass/silica, consisting of a tube, 300 mm in length closed

at one end, with a side-arm near the open end and with dimensions and tolerances as given.

There should be a slight taper in the bore of the tube so that it is little wider at the open end than

at the closed end.

Receivers

Tar cooler C is a U-shaped hard glass tube with its inlet limb closely fitting the rubber bung

attached to the side arm of the retort and outlet limb extended and bent to allow for connection

with the ammonia scrubber D downstream. It is provided with a bulb (at the bottom) of capacity

of at least 5 ml for receiving the condensed products and a stopcock which allows their removal

when required. The tar cooler is supported suitably and cooled externally by immersing in a tall

glass beaker/jar containing cold water or ice.

Distance Rod

To gauge the length over which the sample is spread in the retort tube. It may be in the form of abrass piston or of a rubber bung mounted on a glass rod. The end fits loosely in the bore of the

retort.


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RETORTFORGRAY-KINGTESTElectrode Carbon

To comply with the following requirements:

Retained Percent

Screen analysis:On IS Sieve 20On IS Sieve 12 and passingthrough IS Sieve 20,MaxOn IS Sieve 6 and passing

through IS Sieve 20Passing through IS Sieve 6

Nil26

10 to 40

50 to 85

Moisture, air-dried basis 1.0

Volatile matter, less moistureair-dried basis, Max

1.5

Ash, Max 5.0

Bulk density 1.00 to 1.03g/ml at 25OC


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Specific gravity 2.05 to 2.09

Ammo ni a Scrubber

TAR COOLER AND AMMONIASCRUBBERD is a hard glass tube fitted with a stopcock at bottom and an inlet limb. The scrubber is chargedwith dilute sulphuric acid (about 6 N) to absorb ammonia gas. The closely fitting rubber bung at

the top of the scrubber is provided with a bent glass outlet tube which in turn is connected to the

gas-holder through the stopcockL.

Gas Holder

E is a 5 litre aspirator bottle, filled with a mixture of glycerine and water (50 : 50 by volume) and

a few ml H2SO4, (specific gravity of the mixture 1.15 approx). The gas holder is connected

through the stopcock H by rubber tubing to a freely suspended glass reservoir G using a pulley

.A glass vessel containing lead block counterbalances the reservoir.

When gas enters the gas holder through the stopcock L the displaced liquid flows into the glass

reservoir G, from where the overflow liquid falls into the glass container K. If the internal

diameter of the container K is equal to that of the gas holder E, any fall in the liquid level in E

causes an equal rise in the liquid level in the container K. The counterpoise J floating on the

liquid in the container K rises with the liquid level. Consequently, the reservoir is lowered to the

extent of the rise of counterpoise J, thereby maintaining a constant pressure automatically


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throughout in the gas holder E. A mild suction required for the easy flow of gas may be

maintained by suitably adjusting the height of the reservoir. The stopcocks L and M on both

sides of the gas holder serve to isolate it from the system and thereby contained gas at the end, of

the experiment. The water level in the limbs of manometer F shows the difference in the

pressures of gas in gas holder E and that of the atmosphere. The thermometer N, fitted to the gas

holder E, serves to measure the temperature at which the gas is collected.

Barometer

To measure the atmospheric pressure prevailing at the time of the experiment.

Clock or Watch

Indicating both minutes and seconds.

Preparation of Coal Sample

The coal is air-dried and ground to pass IS Sieve 20 (21 microns) preferably with a laboratorymechanical mixer.

Precautions for Rapidly Deteriorating Coking Coals or Oxidising Coals

The coking properties/propensities of some coals deteriorate rapidly when they are exposed to

air, and in all strictly comparative work, precaution should be taken to obviate this deterioration.

Storage in sealed containers under water or with the air replaced by nitrogen, are recognized

methods. Since certain coals are very liable to oxidation it is important that the coal should not

be heated above normal room temperature at any stage in the preparation of the sample.

Procedure

Two techniques are followed depending upon the types of coal under investigation.

Technique I -Applicable to Non-swelling and Moderately Swelling Coals

Giving Cokes Up to and Including Type G2

a. Determine the moisture content of the air dried coal sample. Weigh 20.00.1 g of coal on

a scoop and transfer without fouling the side-arm, into the main body of the retort which

is held almost vertically. Brush into the retort with a small soft brush any coal adhering to

the scoop. Turn the retort into a horizontal position with the side arm downwards and the

distance rod inserted so that the face of the piston is 150 mm from the closed end of the

retort. Hold the open end of the retort and the positioned distance rod in one hand and the

closed end of the retort in the other. By careful shaking, spread the coal into an even layer

over the 150 mm length, and then lightly consolidate by tapping the retortion the bench.

Carefully push back any coal which may have crept past the distance rod, on to the main

body of the coal by careful strokes of the distance rod itself. Re-level, consolidate again

and withdraw the distance rod. Alternatively, a plug of ignited asbestos wool is inserted


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into the retort (after dropping coal into the retort and leveling the same) at 150 mm from

the closed end. Gentle tapping help smoothen the coal layer. Close the open end of the

retort by means of a soft rubber or neoprene bung. Clean and dry the tar cooler, keep a

small wad of burnt asbestos wool in its outlet limb (the wad of asbestos wool prevents the

escape of tar vapours) weigh and attach to the side arm of the retort. Fill the ammonia

scrubber D with dilute sulphuric acid (6 N) till the glass beads are completely drenched.

Fill the gas holder E completely with glycerin/water mixture. Adjust the level of reservoir

G so that top of the overflow tube is slightly below the level of the liquid in the gas

holder E to develop mild suction. Weigh the container K and place it in position. Clamp

the assembly, namely retort B, tar cooler C, ammonia scrubber D, gas holder E, gas

reservoir G, container K into position.

b. The furnace, previously raised to a steady temperature of 325OC, rests on the frame

behind the retort and is screened from it by a piece of asbestos board. Remove the

asbestos board and draw the furnace smoothly and quickly over the retort. Start the

timing from this instant, and increase the heating current by a pre-determined amount togive,as nearly as possible, a regular rise in temperature of 5C per minute.

c. The tolerances for the temperature control are as follows:

Heating rate 5C 1C per minute

Temperatureat any instant

300C + 5t 10C where tis the time in minutes fromthe start of heating of the coal

d. When the furnace is drawn over the retort, the temperature drops to about 300OC and then

starts to rise at approximately the required rate of 5OC per minute. At the end of the fifth

minute it may not be exactly 325OC, but this temperature must be attained within a range

of 3 to 7 minutes from the start.

e. Consider the re-attainment of 325OC as the 5 minutes datum line and reset the clock

accordingly. Thereafter maintain the regular increase in temperature of 5OC per minute

by small increase of current at approximately regular intervals of time, the temperature

being observed every two or three minutes.

f. Observe and note down the gas point and oil point, that is, the temperatures at which

the evolution of gas commences and oil vapours first appear respectively. When the

temperature reaches about 590OC reduce the current to that required to maintain the

furnace at 600C. The thermal inertia of the apparatus is usually sufficient to carry thetemperature from 590OC to 600OC in the final two minutes. Hold the furnace at this

temperature for further 1 hour always cautiously maintaining the pressure level in the

manometer.

g. Pipette out some liquid from the container K and allow to flow into the glass reservoir G

raising it slowly till the top of the inlet is at the same level to that of the liquid in the gas

holder E and the manometer F is leveled. Return the unused liquid to the container K.


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Record the temperature (T1) as shown by thermometer N and the pressure (P1) as shown

by the barometer. Close stopcocks L and M, withdraw the furnace, detach retort B from

the tar cooler C and allow the retort to cool.

h. Coke type and yield - When the retort is cool enough to handle, weigh it along with the

rubber bung. Remove traces of tar sticking to the mouth and side arm of the retort and the

rubber bung by burning off in a blowpipe flame or by solvents. Record the mass of tar

removed from retort. Also record the yield of coke residue.

i. Gently slide carbonized residue out of the retort and compare it with standard coke types

and assign appropriate coke types. If coke type obtained is above G2 repeat the assay by

following technique II applicable to swelling coals.

j. Tar yield - Clean and weigh tar cooler C. The increase in mass represents the combined

yield of tar, liquor and moisture from coal. In order to obtain yields of tar and liquor

separately wash down contents of the tar cooler with benzene into a 10 ml measuring

cylinder. Measure the volume of the aqueous layer and convert to grams assuming

specific gravity of liquor to be 1.0. Record this mass as mass of liquor plus moisture fromcoal. Deduct the mass so obtained from the combined mass of tar liquor and moisture

from coal to get the yield of tar and then add the mass of tar removed from retort to get

the total yield of tar.

k. Liquor yield - The yield of liquor is obtained by deducting 1/5th of the percentage

moisture of coal from the combined mass of liquor plus moisture from coal.

l. Ammonia yield - Wash down contents of ammonia scrubber with distilled water and take

it along with the aqueous layer from tar cooler into a distillation flask and make up the

volume with sufficient distilled water. Clamp the flask into the distillation apparatus,

make the contents alkaline by adding 100 ml of sodium hydroxide solution (40 percent,

m/v), distil and estimate ammonia as given in IS 1350 (Part 4/Set 2):1975.A singledetermination will suffice.

m. Gas yield - Weigh container K along with the collected liquid. The increase in mass

represents the mass of liquid displaced by the gas collected in gasholder E. Measure the

specific gravity of liquid with a hydrometer. Calculate the volume of gas.(Alternatively,

the gas volume can also be estimated by measuring the volume of the displaced liquid

itself). Record temperature of gas and atmospheric pressure. Note the vapour pressure at

that temperature and subtract this to arrive at the correct pressure. Calculate the volume

to NTP (saturated) that is, OC and 760 mm Hg (saturated).

n. The cooling of the furnace after the test can be hastened by placing in it a suitable iron

rod or a water cooled tube. After the removal of tar and coke from the retort, it is only

necessary to wipe out the inside of the retort with a cloth to clean it ready for the next

test.


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Technique II -Applicable to Swelling Coals, Giving Cokes Above Type G2

a. A different technique is used for coals giving a coke that is swollen to a volume much

greater than that of the original coal. Here the classification is based on the minimumproportion of electrode carbon or coke breeze which is necessary to add to the coal to

control the swelling.

b. A first rough guide to the correct blend is given by the following table relating crucible

swelling numbers and (LT) Gray-King Assay coke types although it must be appreciated

that there are many and striking exceptions:

Crucible Swell ing Number (LT) Gray-King Assay Coke Type

0 AB

1 - 4 CG2

4 - 6 FG46 - 8 G3 G98 - 9 G7 or above

In this table, the subscript figure to the letter G gives the number of parts of electrode

carbon or coke breeze in 20 parts of that coal-electrode carbon or coke breeze mixture

which gives a coke of type G. In all the trials carried out by this technique,20 0.2 g of

the mixture are carbonized, consisting of a quantity of electrode carbon or coke breeze,

say x 0.1 g and (20 - x) 0.1 g of the coal. The quantities are weighed separately and

thoroughly mixed by shaking and rotating for 5 minutes in a screw capped jar of about

100 ml capacity. The whole of the 20 g mixture is then transferred to the retort and

carbonized as described for non-swelling coals. Two or more assays on different blendsare usually necessary to make a precise assessment of a swelling coal.

Conduct the assay in duplicate and take average of the corresponding yields of the products.

Carry out blank determination using electrode carbon or coke breeze, other procedure of the

experiment remaining the same. Deduct the volume of gas (that is, displaced air converted to

NTP) from the volume of gas obtained at NTP.

Tolerance

Degree of accuracy of the method is 0.2 percent of the coal for the yields of coke, tar and liquor

and 125 ml per 100 g of coal for the gas volume.


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TYPES OFC OKEF XOMG RAY-KINGA SAY


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The maximum dilatation value is the key parameter and for individual coals, the highest valuepossible is considered optimal:

High volatiles: +50 to >300%.

Medium volatiles: +100 to 250%.

Low volatiles:


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CO2 is not available in large quantities

Difficulty of interpreting atmospheric analysis results.

Combustion gasesCombustion gases generally known as Gaseous Combustion Products (GCP), contain a

significant proportion of N2 along with CO2, CO, water vapour and certain other constituents.GCP are generally low in O2 (0.74 to 0.40% by volume).

The use of combustion gases for fire fighting has many advantages in terms of cost and

efficiency.

Some of the important points are as follows:

It can be generated on site; independent of commercial suppliers

It can be generated at high rates of up to 1800 m3/min.

It carries large water volume as steam into the fire zone which has a cooling effect.

However, it could lead to water-gas reaction which vigorously promotes, rather thaninhibits combustion and results in very hot fires.

The following disadvantages are attendant with the application of combustion gases (GCP) for

fire fighting.

The gases need to be cooled before pumping into the fire area.

Monitoring the state of the fire is done by analysis of gas samples from the fire area, so

that such monitoring is seriously compromised by the presence of GCP gases used.

NitrogenN2 can be delivered into fire area in liquid form from a tanker or in gaseous form through airseparation unit/evaporation unit via piping arrangements.

There are several advantages of using N2.

The N2 is cold and dry and poses no problem with cooling or compression, as is the case

with other processes where the gas is produced by chemical reaction or by catalyst.

It is simple to deliver liquid N2 on-site and the safety aspects are good.

It can be gasified in a vaporizer with a rated output of up to 300 m 3/min. and this can be

increased even further by operating multiple vaporizers in parallel.

However, the system also has some disadvantages.

It is impractical to store the gas over long periods. Therefore, it is sometimes very

difficult to obtain a sufficient quantity of N2 if large amounts (i.e. more than 300 m3/min.

for several days) are needed. This may occur when there are several fires at the same time

or if there is a really big fire.


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atmosphere or can be used in a combustion process to enhance combustion efficiency. The N2

flow thus generated is continuously checked by an O2 analyzer to determine the oxygen content.

Advanta ges

The membrane system operates at a constant pressure with no change-over cycles which

results in consistent gas purity at the outlet of the module. The chances of sudden failureis absent.

The operating pressure of the system is 11 kg/cm2. It thereby eliminates the need for a gas

booster which results in a saving on capital, spares inventory, maintenance.

O2 enriched air of 40% purity is available as a byproduct from the outlet of the membrane

module. The enriched oxygen can be used for assisted combustion or waste water

treatment.

This system is much more compact, leading to space saving and lower expenditure on

civil construction.

This system is not affected by changes in the ambient temperature and the operation is

noise free.

Disadvantage

Initial capital cost is very high, at least three times that of PSA type N 2 generator. It is the main

reason why the nitrogen generator is not generally favoured.


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Pumped gas requirements

Pumped gas requirements are determined by the rate at which air leaks into the fire area. As far

as possible, air leakage should be prevented to ensure minimum gas requirements. Air leakage

rate depends upon several factors such as:

the difference in pressure inside and outside the sealed area which is caused by pressure

losses in the adjoining ventilated mine workings.

the buoyancy pressure developed by density differences between sealed and unsealed

mine atmosphere.

Absolute air pressure changes caused by barometric pressure variations at the surface of

the mine.

In the first two instances, pressure differences can be reduced by equalizing the pressures in the

adjoining mine workings, adjusted for possible buoyancy pressures. Barometric pressure

variations cannot be reduced by equalizing ventilating pressures in adjoining mine workings, butby equalizing pressures across the seals. It calls for a pressure balancing chamber. The chamber

is formed by building a thin brick stopping 2 m outside of the isolation stopping. Two pipes are

laid to connect the pressure chamber to the main intake as well as return airways. Differential

pressure across the seal is adjusted by airflow through these pipes.

To calculate the concentration of N2 required to control the fire in a sealed area, consider a sealed

panel which is subjected to a sustained unidirectional leakage and a substantial inflow of external

gases (such as methane) from the surrounding strata. After a time, the concentration of N2 inside

the sealed panel can be given as below:

Where C3 = (QL+QN+QG)/Vand C4 = (Na.QL+QN)/V

QL is leakage into the panel at temp. T3 (m3/sec), QNis rate of N2 injection at temp T3 (m3/sec), V

is volume of sealed panel (m3), N0 is initial concentration of N2 in the panel (fraction), Na is

concentration of N2 in the ambient air outside the panel (fraction), QG is inflow of external gas at

temperature T3 (m3/sec.), T3 is average temperature inside the panel (oK).

Equation [1] can be used to derive the concentration of N2at any given time after the start of N2

injection provided reasonable estimates ofQLand QGcan be made. The maximum concentration

of N2gas for a given set of conditions can be determined from the Equation [1] if t


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Schematic plan view diagram of the GAG 3A Jet Engine System

There maybe production of isobutene and isopentane dependent on fuel grade and additives but

these will be at low levels. Volumetric flows from the system have been stated in the literature in

the 50,000 cfm range, and as high as 64,000 cfm. However, the volume of the engine output is

susceptible to the site specific backpressures experienced in a mine inertisation application. It is

thought that these backpressures are a function of mine ambient temperature, gas mixture and

buoyancy effects, barometric fluctuations, and mine resistance to air flow. While it was not

possible- in the U.S. applications that follow- to accurately measure the volumetric GAG 3A

system output, most observers felt that output was below this level. High backpressures,

experienced at times during these applications, were probably the main reason for this

conclusion.

A specially designed afterburner (part of the engine in figure ) is utilized to achieve near

stoichiometric combustion(complete consumption of O2). This is achieved by varying fuel

pressure, engine speed (air intake), and water cooling the tubes which contain the flame. The

heat produced by the afterburner is as high as approximately 1,300 F in the chamber and

temperatures of almost 3,200 F have been recorded at the flame tip.

A diffusive cooler (figure ) is utilized to serve a two-fold purpose.

Provide a barrier between mine atmosphere and the GAG system. Maintained between

critical maximum and minimum pressure requirements, so as not to impinge on the water

curtain and create O2.

Cool the exhaust gases prior to mine injection, typically to a 160F to 190F temperature

range.


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13 and 14 seams, leading to deterioration of condition of the fire. Central Mining Research

Institute (CMRI), Dhanbad, India was commissioned to investigate the recurring problem of

fighting mine fires which had adversely affected the production of mine for many years and to

find suitable practical solutions. CMRI, after detailed investigation and computerized planning,

advised the management of mines to opt for Dynamic Balancing of Pressure for some portions of

the mine and recommended procurement, installation and commissioning of a 500 m3/hr.

capacity N2 gas generator (PSA type) for fire control purposes.

Measures to implement and adopt Dynamic Balancing of Pressure yielded encouraging results.

The fire was brought under control in most parts of the mine. However, at a few places in the

sealed-off area, O2concentration did not fall to the desired level. This was attributed to existence

of an air leakage path extending beyond the pressure balancing zones. In view of the results, it

was recommended that a N2 generator be installed to inject gas into the sealed off area. Based on

the existing conditions, the capacity of the plant and injection rate was calculated and a 500

m3/hr. PSA N2 gas generator was procured and installed in April 1997. The injection of N2gas at

6 points at a time resulted in a dramatic reduction of O 2concentration which had in most places

reached a level exceeding 98%. For further improvement in the condition of the mine, it was

suggested that a second identical N2flow to 1000 m3/hr. in the mine, but will assist in maintaining

an uninterrupted supply of N2 during any breakdown or maintenance of one of the units.

However, dynamic balancing of pressure should be practiced throughout the life of the mine.

The first plant is showing encouraging results yielding 99.3% purity of N 2. In a total void area of

8 million m3, 7 million m3of N2has been injected to date.

GDK - 9 incline, Singareni Collieries

GDK 9 incline is one of the highly mechanized and highly productive collieries in theRamagundam area. Large scale use of liquid N2 was made in 1986 at Godavarikhani No.9.

Incline of Singareni Collieries Company Ltd to combat a blazing underground fire. The intensity

of the fire was so severe that the mine management staff was compelled to seal the mine from the

surface. Liquid N2helped in extinguishing of the fire, cooling the atmosphere and conditioning it

so as to be non-explosive. It took 125 days to reopen the mine and restore it for normal

production . The whole mine had been sealed off due to fire affected panel Nos. 8 and 8A. These

panels were at a depthranging from 30 m to 40 m. Stoppings of the panels as well as few

stoppings at panel No. 7, were damaged and subsequently an explosion occurred. Mine

management was faced with the problem of recovering equipment worth $ 4.18 million. The plan

of operations for combating fire was as follows :

Building concrete plugs around fire-affected area in No. 3 seam from surface

N2 injection

Blanketing of subsided areas from surface

Sampling and monitoring the atmosphere in sealed areas

Establishing chemical analytical laboratories at the mine.


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a mutual response arrangement between the mines to ensure operational capability in the event of

an extended incident at any of their operations.

Sugar Run Bottom and slope area at the Loveridge Mine

After some direct fire fighting attempts, the Loveridge Mine was evacuated, the mine openings

sealed, and six boreholes drilled in and around the fire area for monitoring and water pumping.

By March 2003, attempts to suppress the fire with water pumped from the surface was not fully

successful due to existing floor elevations that limited uniform and complete water dispersal

through the fire area. In addition, there were concerns that there was sufficient air leakage

through the mine opening seals to keep the fire in a presumed smoldering state. A decision was

then made to attempt to inert the fire area using the GAG 3A jet engine technology. A ventilationsimulation of the inertisation situation at Loveridge Mine was done by the operator, which

concluded that it was feasible to inert the whole mine.

The slope, initially sealed with a make-shift seal, would permit the inert gases to travel to the

fire area near the slope bottom and continue through the main entries of the mine to the other

shaft areas.


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By April 4, 2003, the GAG 3A system had arrived at the Loveridge Mine site and, after some

maintenance to the jet engine and its components, the system was commissioned for inertisation

operations.

In total, the engine operated for 270 hours with minor servicing and replacement of consumable

parts and the engine consumed an average of 423 gal (1,600 liters) of fuel per hour and 4,887 gal(18,500 liters) of water per hour.

GAG 3A jet engine and afterburner, Loveridge Mine

Pinnacle Mine

At the Pinnacle Mine located near Pineville, WV, a series of four explosions occurred between

August 31 and September 16, 2003 in the active #8 longwall district, shown in figure 9. Mine gas

readings from the various monitoring boreholes indicated that there was active combustion

ongoing at an unknown location in the longwall district. The operator began drilling additional

boreholes into the longwall gate roads to detect the heat source. Phoenix First Response was

contacted by the operator and arrangements were made to utilize the GAG 3A jet engine in an

attempt to inert the approximately 9,000 ft by 9,000 ft longwall district to extinguish the fire.

Arrangements were also made to have trained GAG operators from Poland man the operation ofthe jet engine. By October 1st, the engine had been set up at the 8A bleeder shaft and the

operators had arrived. The engine was started late in the day after a crane had removed the

bleeder fan elbow conduit from the shaft and replaced it with a specially designed GAG docking

hood that was then fastened to the shaft coping.


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References Indian Standard:1353, 1993, Determination of caking Index, Bureau of Indian Standards, New

Delhi.

Fighting mine fires using gases with particular reference to nitrogenby S.K. Ray, A.

Zutshi , B.C. Bhowmick, N. Sahay, and R.P. Singh http://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-

WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdf

COAL MINE INERTISATION BY REMOTE APPLICATIONBy T. P. Mucho ,I. R.

Houlison , A. C. Smith, and M. A. Trevits
http://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdfhttp://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdfhttp://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdfhttp://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdfhttp://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdfhttp://www.sgs.com/~/media/Global/Documents/Flyers%20and%20Leaflets/SGS-MIN-WA058-Lab-Testing-Metallurgical-Coal-and-Coke-EN-11.pdf