impact of coal beneficiation on rail transport in india

This article was downloaded by: [University of Windsor]On: 25 September 2013, At: 21:27Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Coal PreparationPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/gcop19

Impact of Coal Beneficiation onRail Transport in IndiaS. Bhattacharya a & Ashim Kumar Maitra ba Department of Fuel and Mineral Engineering,Indian School of Mines, Dhanbad, Indiab Howrah Division, Eastern Railway, Howrah, WestBengal, IndiaPublished online: 20 Jun 2007.

To cite this article: S. Bhattacharya & Ashim Kumar Maitra (2007) Impact of CoalBeneficiation on Rail Transport in India, Coal Preparation, 27:1-3, 149-166, DOI:10.1080/07349340701356300

To link to this article: http://dx.doi.org/10.1080/07349340701356300

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,

http://www.tandfonline.com/loi/gcop19

http://www.tandfonline.com/action/showCitFormats?doi=10.1080/07349340701356300

http://dx.doi.org/10.1080/07349340701356300

sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

http://www.tandfonline.com/page/terms-and-conditions

IMPACT OF COAL BENEFICIATION ON

RAIL TRANSPORT IN INDIA

S. BHATTACHARYA

Department of Fuel and Mineral Engineering,Indian School of Mines, Dhanbad, India

ASHIM KUMAR MAITRA

Howrah Division, Eastern Railway, Howrah,West Bengal, India

Thermal coal, which is the mainstay of India’s power generation,

contains as high as 50% ash. To meet the rapidly growing demand

for thermal power, the transportation facilities need to be signifi-

cantly expanded. Major routes of Indian Railways are currently

saturated. Creation of transport infrastructure is expensive. Benefi-

ciation of coal is known to improve its quality and consistency.

The present work examines the impact of beneficiation on thermal

coal transportation by railways and finds that it would considerably

improve the loading capacity of wagons, their life and also ‘‘release’’

carrying capacity on the saturated rail network.

Keywords: Coal beneficiation impact; Rail transport

Received 26 April 2005; accepted 21 February 2007.

University Grants Commission through its Special Assistance Programme has sup-

ported part of this work. The views expressed in this article are those of the authors and

do not necessarily reflect the views of the Ministry of Railways, Government of India.

Address correspondence to S. Bhattacharya, Department of Fuel and Mineral Engin-

eering, Indian School of Mines, Dhanbad 826004, India. E-mail: [email protected]

Coal Preparation, 27: 149–166, 2007

Copyright Q Taylor & Francis Group, LLC

ISSN: 0734-9343 print=1545-5831 online

DOI: 10.1080/07349340701356300

Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

INTRODUCTION

Access to energy is one of the crucial parameters determining the rate of

economic growth of a developing nation. India is no exception. At

present, the energy consumption in India is only 479 kg of oil equivalent

per capita. This is low even compared to some of the developing coun-

tries, e.g., China. More than 60% of Indian households still depend on

traditional biomass-based sources of energy like fuel wood, dung, and

crop residues for meeting their cooking and heating needs. In view of

the current growth rate of 6.5–8.0–9.0%, the requirement of commercial

energy of India is projected at about 412 and 554 million tonnes of

oil equivalent (MTOE) in 2007 and 2012, respectively [1]. Increase in

demand for commercial energy would imply, in the case of India, an

increase in the demand for fuel transportation. With commercial fuels

replacing the traditional noncommercial fuel sources, the overall demand

for coal would also rise sharply.

India is endowed with large energy resources, both exhaustible

(particularly coal), and renewable energy resources. Despite the

resource potential and the significant rate of growth in energy supply

achieved over the last few decades, India continues to face serious

energy shortages. This has led to reliance on increasing imports for

meeting the demand of oil, gas, and coal, in particular, oil and coking

coal. Currently only about 30–33% of India’s oil demand is met from

indigenous production. In contrast to oil and gas, coal prices are low

and quite stable. Coal transportation is easy and safe. Because of abun-

dance of indigenous resources, there is no uncertainty about its supply.

Coal therefore, despite its indigenous poor quality, remains the pre-

dominant source of energy amongst India’s primary energy resources.

Based upon the production level of the calendar year 2000, Indian coal

reserves are forecast to be exhausted after 233 years, whereas oil and

natural gas are forecast to be consumed after 15 and 33 years, respect-

ively [2]. India’s currently remaining extractable coal reserves stand at

12,300 MTOE based on proved reserves and another 9,020 MTOE

based on inferred and indicated reserves [3]. Efficient utilization and

distribution of coal therefore is crucial to India’s quest for additional

energy.

Indian Railways (IR) is the principal transporter of coal in the coun-

try. Coal is beneficiated to improve the quality of coal delivered to the

market. To evaluate the benefits of beneficiation for transportation, it

150 S. BHATTACHARYA AND A. K. MAITRA

Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

would be necessary to examine and to evaluate the effect of beneficiation

on coal quality and the resultant impact upon carrying capacity in the

context of the existing condition of the rail network and the anticipated

future demands for coal transportation.

INDIAN RAILWAYS AS THE BULK CARRIER

For every percentage point increase in the growth rate of the Gross

Domestic Product (GDP), total demand for transportation is expected

to increase by 1.25%. Therefore, the targeted annual rate of economic

growth of 8% would imply a growth of overall transport output by

10%. Transport being an energy intensive activity, such rapid growth

would imply a very sharp increase in energy demand. The railway is

recognized as being four times as energy efficient as road transport.

Almost 90% of the freight carried by IR is bulk freight traffic, with coal

contributing around 45% of the total. The other bulk commodities car-

ried are: indigenous raw materials to steel plants (8%), finished steel

(3%), iron ore for export (5%), petroleum products (6%), fertilizer

(5%), cement (9%), and food grain (8%) [4].

At present, the share of coal in the total energy consumption of the

industrial sector in India is nearly 72.5%. In the case of power gener-

ation, the coal-fired thermal route accounts for 59% of the power gen-

erated in the country [5]. The same route is likely to retain its

predominant share in the foreseeable future because of the significantly

shorter lead times needed to build coal-fired plants, fluctuating and

high prices of imported oil and gas, hydroelectric power generated

being seasonal outside the core Himalayan region, and also because

of the opposition from environmental groups to hydroelectric and

nuclear plants. Limited availability of indigenous uranium ore is

another constraint. Installed capacity for power generation is expected

to rise from the present level of 100,000 to 200,000 MW by 2012. With

the demand for power coal growing at such a rapid rate (Table 1), the

movement requirement by rail would also increase rapidly. Currently,

about 70% of the coal transported by IR is for the power sector, which

is expected to increase substantially in the future. The remaining 30%

consists of essentially coking coal for integrated steel plants and a rela-

tively small amount of noncoking coal for sponge iron, cement, paper

plants, etc.

RAIL TRANSPORT IN INDIA 151

Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

COAL QUALITY

The present assessment of coal resources in India [6], as of the beginning of

2004, was approximately 246 Bt (Table 2), of which about 87% is being cate-

gorized as noncoking (thermal) type. About 80% of these thermal coals are

of inferior grades with ash contents of 24–45%. The share of such inferior

coal is expected to increase progressively. The ash content in coal as deliv-

ered to power plants currently averages above 40%. With few exceptions,

the majority of coal-fired power plants receive coal from more than one

source. As most of the plants do not yet have blending and homogenization

facilities, the multiplicity of supply sources adds to the problem of inconsist-

ency in coal quality. Table 3, based on a sample of 43 thermal power stations

over a period of three years, shows that 59% of plants receive coal with more

than 35% ash, while 84% receive coal with at least 30% ash [7].

COAL MOVEMENT BY INDIAN RAILWAYS

The Indian Railways is the main transporter of coal to the industrial con-

sumers, moving approximately 65% of the coal produced in the country.

The projection of coal demand for 2011–2012 is 620 Mt [8]. If IR’s share

of total coal transport remains at the same level, the demand for coal

movement by rail in 2011–2012 would be 407 Mt, an annual growth rate

of 6.2% between 2003–2004 and 2011–2012, higher than 5.7% achieved

Table 2. Coal reserves by category (Bt) as on January 1, 2004 [6]

Types of coal Total Proved Indicated Inferred

Coking 32 17 13 2

Noncoking 214 75 103 36

Total 246 92 116 38

Table 1. Power coal demand [5] and compound growth rate

Year Demand (Mt) Year Growth rate (%)

1996–1997 214 1996–1997 to 2001–2002 4.39

2001–2002 266 2001–2002 to 2006–2007 5.39

2006–2007� 345 2006–2007 to 2011–2012� 7.72

2011–2012� 502

�Projected.


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

between 1999–2000 and 2004–2005. Further, if the share of coal in the

total freight loading remains constant at around 45%, as it is today,

IR’s total freight loading in 2011–2012 would have to be 904 Mt. This

represents a growth of 346 Mt in 8 years. Thus, the freight loading would

have to grow at 43 Mt per year at the rate 6.2% per year. The IR system

would thus face a formidable challenge of raising the growth rate of

freight loading. If the rate of economic growth picks up, it is conceivable

that the demand from all sectors of the economy would further rise. Such

growth in demand for rail transport would generate massive pressures

on the IR network most of which is already saturated.

Major arterial routes of IR are currently saturated. Route kilo-

meters, i.e., the distance covered by the rail track between two points

(A and B) have increased only 1.18 times in the last 55 years. Running

kilometers, which include the element of double=multiple lines between

two points have increased only 1.41 times. During the same period, one

tonne of payload moved over one km distance (Net Tonne Kilometer or

NTKM, a standard measure of transport output) increased by 8.71 times

and one passenger moved over the same distance (Passenger Kilometer

or PKM) increased by 7.28 times [4]. Unlike many railroads in the

developed economies, IR run passenger and freight trains on the same

track. The difference in the speeds of the two types of trains erodes

the capacity utilization of the track.

The network congestion is further aggravated, as the preponderant

share of the traffic is concentrated on about a dozen routes. The six

routes connecting the four metropolises of Delhi, Mumbai, Kolkata,

and Chennai, also called the Golden Quadrilateral (GQ), comprise

16% of the network kilometres, but carry 65% of the freight and 55%

of the passenger traffic (Figure 1). The eastern region of India has nearly

70% of the total coal reserves. The skewed pattern of distribution of coal

deposits and regional imbalance in the demand for power coal compli-

cates the transport requirement with demand increasing from all corners

of the country. GQ routes carry 70% of the power coal moved from

indigenous sources. In the year 2003–2004, out of 173 Mt of power coal

Table 3. Ash range of coal received by various power plants [7]

<25% 25–30% 30–35% 35–40% 40–45% >45%

2 (5%) 5 (11%) 11 (25%) 12 (28%) 8 (19%) 5 (12%)


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

moved by IR, 55.4 Mt was in the Kolkata–Delhi segment of the GQ. The

congestion actually gets further aggravated because of the movement of

imported coal. Imports have not been considered for the present analysis

as indigenous sources provide the preponderant part of the noncoking

coal consumed. Keeping the present trends in view, the estimated future

demand including that by captive power plants has been divided into

Figure 1. Important rail routes, major coalfields, and thermal power stations.


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

distance segments to assess the transportation requirement (Table 4).

The focusing question is, therefore, ‘‘Does coal beneficiation, in view

of the existing congestion of the arterial routes, offer a viable solution

towards reducing pressure on the IR network?’’

BENEFICIATION OF POWER COAL IN INDIA

Beneficiation of power utility coal is a relatively new development in India.

Currently, there is a combined noncoking coal washing capacity of 50.15 Mt

per year. It is proposed to add another 21.5 Mt within the next few years [9].

India’s noncoking coal production, however, stood at about 325 Mt for the

year 2005–2006 and is targeted at about 350 Mt for the year 2006–2007,

which is about seven times the installed washing capacity [10]. At present

only nine power stations receive a total of about 15 Mt of washed coal

per year, the remaining plants using only run-of-mine (ROM) coal [8].

Out of 15 Mt, about 8 Mt is transported on the Kolkata–Delhi GQ route

alone. Power coal washing in India is carried out to target <34% ash, unless

otherwise specified, and generally provides a clean coal yield of 70–80%.

Washing is shallow (partial) because of the mandatory use of coal with only

<34% ash at all power stations located more than 1000 km away from the

coal sources and also for those located at urban and environmentally sensi-

tive locations. Power coals consumed at the pithead and within a rail dis-

tance of 1000 km, at present, are generally not washed, unless the power

station is located near an urban settlement.

In India, thermal power plants are not yet inclined toward using

washed coal essentially because of the following reasons:

. Emission norms in India are not yet as strict as those in most

developed countries,

. There is little restriction on generation of fly ash, and

. The norms guiding land disposal of fly ash are not very rigid.

Table 4. Distance-wise requirement of thermal coal [8]

Million tonnes

Distance (km) 1996–1997 2001–2002 2006–2007 2011–2012

Pit-head 70 89 99 155

<500 54 51 55 70

>500<1000 35 30 43 60

>1000 km 55 95 148 216

Total 214 265 345 501


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

Annual fly ash production in India in the year 2004 stood at 100 Mt and

by 2012 it is expected to rise to 175 Mt. To encourage fly ash utilization,

the Government of India in 1999 stipulated that for the subsequent 10

years all coal-based power plants would supply fly ash, free of cost, for

the manufacture of cement, concrete blocks, bricks, and tiles and for

the construction of road, embankments, dams, etc. Bricks, tiles, and

building blocks manufacturing units located within a radius of 50 km

of a power plant would have to mix at least 25% ash with the soil. It

was thought that on the strength of this notification in the next 3 years,

fly ash utilization would increase to 30%, and the annual rate of increase

would be 10% for the next six years [11]. In reality however, fly ash uti-

lization in the year 2004–2005 only reached a level of 23.5% of the total

fly ash produced, which was actually half of the set target [12].

The other reason for disinclination to thermal coal washing is the

grade-based pricing mechanism for noncoking coal (Table 5). Ash

reduction, or improvement in calorific value is in itself not sufficiently

justifiable to make noncoking coal washing cost effective, the primary

requirement being to upgrade by 1–2 grades in quality. Because the

majority of the power coal washeries are located in the South Eastern

Coalfields, current prices have been quoted for the same quality. The pri-

cing pattern for coals from other coalfields is similar.

The Useful Heat Value (UHV) is calculated on the basis of an

empirical relationship given by

UHV ¼ 8900� 138 ðAþM Þ; ð1Þ

Table 5. Gradation of noncoking coal in India and current basic price� [6]

Current price (Rs.=tonne; 1 US$ ¼�Rs. 43.00)

Grade UHV (kcal=kg) Non-long flame Long flame

A >6200 1080 1200

B >5600 to�6200 1010 1130

C >4940 to�5600 860 970

D >4200 to�4940 730 840

E >3360 to�4200 600

F >2400 to�3360 470

G >1300 to�2400 350

�Valid for South-Eastern Coalfields only.


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

where A and M are ash and moisture contents, respectively. In the case of

a coal having M < 2% and volatile matter (VM) <19%, the UHV would

be the value arrived as above, reduced by 150 kcal=kg for each 1%

reduction in VM content below 19% level pro-rata.

Washing flowsheets are typically preceded by single- or two-stage

crushing to reduce the ROM coal to a top size of 100, 75, or 50 mm. Crushers

used include single and double roll, sizers, and in some cases rotary breakers.

Small coal (�13 mm,�10 mm, or�6.5 mm) with a relatively low ash is

usually not washed. The selected size would depend upon the ash content

and effectiveness of screening. The coarser fraction is washed by jig or heavy

media bath or heavy media cyclone to the extent that combined ash of

washed coarse coal and unwashed small and fine coal is within the stipulated

limit. In some of the plants, barrel washers and spirals are used for small

(<10 mm) and fine (<3 mm) coal, respectively in which case the fraction less

than 0.5 mm would normally be discarded.

ROM coal obtained from mechanized opencast mines is usually

sized up to�1500 mm, but may be as large as�2000 mm. Coal handling

plants in India crush the ‘‘as-received’’ ROM coal to a nominal size

of�250 mm, as stipulated by Indian Railways, though on occasion,

the maximum size may be up to 500 mm. Crushers used are gyratory

or jaw or roll types, which rarely operate on scalped feed basis. In some

plants feeder breakers are used. After preparation, ROM power coals are

loaded either through low to high to very high capacity (200–2000–

4000 t=h) pithead coal handling plants or directly from the coal stock-

piles using some form of dozer—reclaimer combination. At these

loading points the train is usually weighed after completion of loading.

It is seldom possible to make adjustments if the train is found to be

overloaded or underloaded. The Indian Railways charge penalty freight

for both overloading or underloading.

BENEFICIATION AND TRANSPORTATION

Effect of Clean Coal Yield

Creation of railway infrastructure is expensive and time consuming. Con-

struction of new railway track costs �Rs. 30 million per km (US$ 0.69

million per km) [4]. The movement requirement to power stations

located at distances >500 km from the coalfields would be 276 Mt by

2011–2012 (Table 4). If the overall pattern of movement was assumed

to remain constant, over the next 7 years the traffic on each of the three


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

arms of the GQ would go up by 1.6 times. In view of the typical clean

coal yield of 80%, unaltered payload per train after beneficiation would

provide a savings in transport effort of 20%. For a movement of 276 Mt,

the savings would be 55 Mt, which is the equivalent of 41 trains per day.

Clearly, this would provide immense relief to the saturated network of IR

especially for long distance movement over more than 500 km.

Between April 2003 and March 2004, 29 Mt of coal moved from the

coalfields in eastern India to power stations in northern India. The dis-

tance between the coal-loading point and the power stations varied from

651 to 1569 km. The total transport output generated in NTKM was

about 33,150 M. Of the total, 21.7% was attributable to washed coal.

Thus the remainder, 25,956 M NTKM, was obtained through the move-

ment of ROM coal. If all the coal were beneficiated, the saving at 20%

would have been 5,191 M NTKM. The cost of moving one NTKM

of freight traffic on IR is approximately Rs. 0.51. Thus, the saving in

monetary terms would be Rs. 2,647.56 M, or approximately US$ 61 M.

At an all India level, the projected demand of 276 Mt is to move over

an average distance of 500 km. A saving of 20% over 276 M would be

55 Mt. The total saving in net tonne kilometers would be 55 million�500 ¼ 27.5B NTKM. At a cost of Rs. 0.51 per NTKM, the total saving

in transportation costs would be Rs. 14,025 M (US$ 323 M).

Given the cost of construction of new railway track as Rs. 30 million

per km, the saving in transport costs, with some simplification, would

appear to be notionally equivalent to the construction cost of 467 km

of new track every year. Conversely, new investment for augmentation

of line capacity would be saved.

The unit of movement to power stations is in trains consisting of 58

BOXN type wagons with a payload of 3700 tonnes per train. Thus, 0.74

BOXN train a day moves 1 Mt in a year. A total saving of 55 Mt would

translate to 41 trains per day. If the three arms of the GQ continue to

carry 70% of the power grade coal, beneficiation on 80% yield basis

would result in a saving of 29 trains per day on the GQ.

EFFECT OF DROP IN SPECIFIC GRAVITY

The discussion on effect of clean coal yield has thus far assumed,

implicitly, that the payload per train remains unaltered after beneficia-

tion. It appears however that the washing processes currently used lead

to a marginal increase in the moisture content of the coal and a reduction


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

in the specific gravity. That would imply that beneficiation reduces the

payload per train.

The BOXN wagon carrying coal to power stations has a volume of

56.26 m3 (9.78 m� 2.95 m� 1.95 m). A train has 58 wagons and IR reck-

ons the payload for a typical coal train as 3700 tonnes [4]. The total

‘‘load’’ generated by a coal rake equals the number of wagons times

the density of coal times the volume of each wagon:

Total load per rake ¼ ð58Þ � ðdensity of coalÞ � ð56:26 m3Þ ð2Þ

The specific gravity of Indian ROM coal is generally 1.5–1.7,

depending on ash content. In view of the shallow washing practiced, after

beneficiation for thermal coal the specific gravity usually remains in the

region of 1.5–1.6. Table 6 shows the load calculation results for different

coals. Ash, moisture, and specific gravity of the ROM and washed coal

samples were determined, on an as-received basis, using standard labora-

tory methods [13]. The samples were obtained as subsamples from rou-

tine samples collected at the loading points for grade analysis (Table 5).

All the ten coals (Table 6) are linked to distant (300–1200 km) power

plants. ROM coals belong to Eastern, Central, and Western Coalfields

and those with high ash are typical for the current consignments to

power plants in India. Clean coals belong to Central and South-Eastern

Coalfields and are transported over a distance of 700–1100 km. Top-sizes

vary depending upon the washery flowsheet. Moisture content of these

Table 6. Payloads per freight train before and after beneficiation [13]

Size (mm) Ash (%) Moisture (%) Density (kg=m3) Load (Tonnes)

ROM Coal

�250 25 1.5 1503 4904

�250 30 2.0 1552 5064

�250 35� 2.0 1610 5254

�250 40� 2.5 1660 5417

�250 45� 2.2 1720 5613

Clean Coal

�100 33 8 1524 4973

�100 32 10 1508 4921

�100 32 10 1512 4934

�50 33 7 1530 4993

�50 33 5 1541 4855

�Typical for the current consignments.


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

clean coals reduces by about 3–5% between the loading and unloading

points, though the same may not necessarily happen during the monsoon

season. Marginal seasonal variation in density arising out of seasonal

variation in moisture content and the effects of differences in size consist

of the consignments, if any, on long distance transportation have been

ignored.

The calculated payload varies from 5,613 tonnes for coal with 45%

ash, 3% moisture, and�250 mm size to 4,855 tonnes for beneficiated

coal having 33% ash, 5% moisture, and�50 mm size. Clearly, the pay-

load per train after beneficiation would be substantially more than what

is posited by IR as the carrying capacity, for typical Indian coals trans-

ported over long distances. The results, therefore, indicate that the pay-

load after beneficiation can be as much as 35% higher than the carrying

capacity stipulated by IR. The results also indicate that dry beneficiation

would raise the payload even further. This is an important area for

further research, particularly for short-distance transportation. The

results of the study are currently being validated with data from a larger

cross section of mines and different varieties of coal. The BOXN wagon

used by IR to transport coal has a load of 21.75 tonnes per axle. The

gross load of the wagon including its own weight cannot exceed

87 tonnes. The payload is constrained by this element. If the load per

axle could be increased, a wagon could carry as much as 87 tonnes of

beneficiated coal, especially with controlled loading. This would lead

to immense savings in transport capacity and investment requirements.

Effect of Washing on Abrasiveness

Coal is known to be an abrasive material leading to high wear rate of

handling and transportation equipment. There are two universally

accepted methods of determining the abrasiveness. In the CERCHAR

method, the grinding pins used for testing have very sharp points, which

can be seen through a microscope. These pins are fitted in a holder and

are allowed to rest on the surface of the coal. The pins are then moved to

scratch the surface within a fixed distance so that pinpoints get blunt.

The distance between the ends of the blunt points is then noted under

a microscope and Vernier calipers. This value when multiplied by 10

gives the CERCHAR Abrasivity Index (CAI). The Yancey, Gear, and

Price (YGP) method essentially consists of rotating four removable

iron-wearing blades in a charge of coal for a fixed number of revolutions


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

and determining the loss in weight sustained by the blades during the

test. Hence, it is reasonable to assume that only those minerals in a coal

that are harder than steel (pins or blades) will significantly contribute to

the abrasive nature of coal.

Generally, washed coal has a lower abrasiveness as compared to the

ROM coal. Abrasive wear is attributable more to the impurities associa-

ted with coal than to the coal substance itself. Removal of impurities by

washing almost invariably should reduce the abrasiveness. Thus, a clean,

well-prepared coal would cover a much narrower range of abrasiveness

than that exhibited by ROM coal. According to Wells et al. [14], the

abrasion index (YGP) is clearly related to the excluded mineral matter

in the coal, but a direct correlation with the ash content is poor. In spite

of significant scatter, the abrasion index can be correlated to the content

of pyrite and quartz. Angular particles were far more abrasive than

rounded particles. This is probably due to rounded particles causing

plastic deformation of the metal surface rather than cutting into the

metal as an angular particle would do. Size, therefore, appears to play

a certain role in the abrasiveness of coal, particularly if it is unwashed.

The larger the size, the more irregular is the shape of the lumps.

This is possibly the reason why the South African state power utility

ESKOM generally demands a 45 mm top size for any coal delivered to

them from washing plants as middlings. For export via Richard’s Bay

on the electrified railway line, the South African coal industry generally

uses a 50 mm top size [15]. On the other hand in Australia, some of the

coals carried by state owned Queensland Rail do not have to travel very

far, less than 300 km. Therefore, wagons rarely appear to suffer from coal

abrasivity related wear. As far as top size selection goes, it is a balance

between yield and moisture and the same is generally�50 mm. It seems

to work well. Some sites do however have larger top sizes, up to 120 mm

to minimize fines [16]. In contrast, for long-distance transportation, the

same company goes by the top size of 50 mm because of such obvious

benefits as reduced wear and tear of wagon bodies, more controlled

and even load distribution, thereby reducing axle and wheel wear and

tear, as well, arising out of reduced abrasiveness. It was also found that

washing by removing harder material that causes wear and sometimes

damage to the wagon bodies, wear and tear on the rolling components,

and also by ensuring controlled loading, improves effective loading and

distribution, thus maximizing the payload. Overall improvement in trans-

portation economics is significant [17]. In this context, noteworthy is the


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

variation in abrasion index of six washed coals and their corresponding

rejects for coals belonging to four different coal basins of the United

States (Table 7). It has also been reported that for US coals, the YGP

index can be as low as 12 and as high as 686, the value for typical sand-

stone being 1210 [18].

As has already been stated, coal transported by rail in India, as

stipulated by IR, has a nominal size of�250 mm, though occasional

maximum size may go even up to 500 mm. This size limit was imposed

only about a decade back when IR introduced the bottom discharge

rapid unloading system. The average Hardgrove Grindability Index

(HGI) of ROM noncoking coals at that time was about 100. It was there-

fore felt that the nominal size limit of�250 mm would ensure controlled

and even load distribution in the wagons. Size-dependent abrasivity of

the coal does not appear to have been given any consideration. Since

then the average HGI of ROM noncoking coals has dropped down to

about 70–80. It has also been observed in recent years that ROM coal,

when crushed to�100 mm with an average ash of not more than 30%,

very rarely shows a CAI greater than 1.1. The CAI determination set-

up, however, imposes a size limit of�100 mm for the lumps to be tested

[19]. Table 8 shows a significant variation in abrasiveness of ROM coals

linked to a coal-fired plant, located in Eastern India [20], where the rail-

ing distance does not exceed 400 km. Such variation is very common and

the coal-railing distance is usually much larger (Table 4). Table 9 shows

how abrasiveness drops on washing the coals at successively lower ash.

Table 7. Abrasion index at 1.60 specific gravity for various types of US coals [18]

Source Weight (%) Ash (%) YGP (mg=kg)

A (Float) 66.8 12.6 13

A (Sink) 33.2 61.6 105

B (Float) 90.7 9.3 45

B (Sink) 9.3 58.3 1515

C (Float) 92.9 5.6 6

C (Sink) 7.1 62.1 351

D (Float) 79.3 9.1 43

D (Sink) 20.7 75.9 162

E (Float) 95.2 6.7 147

E (Sink) 4.8 63.7 1517

F (Float at 1.80) 81.1 7.6 63

F (Sink at 1.80) 18.9 71.8 589


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

Barmuri and Saristhali coals are from Eastern Coalfields, whereas, Ghor-

awari coal is from Western Coalfields [21–23]. The effect appears to be

more pronounced on Barmuri and Saristhali and also on all the four coals

370from the western flank of Jharia Coalfield, which are banded coals and are

from opencast mines where mining dilution by extraneous material is

high. Abrasivity, whether measured by CAI or YGP, generally shows a

substantial increase as and when the ash content crosses the level of 35%.

IR does not yet provide rakes solely dedicated to the supply of coal

375to power plants. Therefore, it would require some more time to make a

Table 8. Abrasiveness of ROM coals linked to a thermal power plant in India [20]

Source Coal field Average ash (%) YGP (mg=kg)

Parascole Raniganj 25–30 18

Bahula 24–26

Dalurbad 22–26

JMT 30–35 150

Ex CHC 94

Lalmatia Rajmahal 36–42 28

Katras Jharia 35–40 80

Pathardih 50

Jarangdih East Bokaro 35–38 40

Table 9. Effect of washing on abrasiveness of�50 mm coal [21–23]

Railing

distance (km)

Washed at ash (%)!Coal#

25 29.5�=30 33.4��=35 40

CAI

400 Barmuri; Opencast;

Mugma Area

1.0 1.1 1.3 1.7

300 Saristhali; Opencast;

Salanpur Area

1.0 1.1 1.4 1.8

700 Ghorawari; Underground;

Kanhan Area

1.0 �1.1 ��1.2

YGP (mg=kg)

1100 Phularitand Opencast; 9.32 12.47 22.68 73.00

Benedih Jharia 16.79 �20.02 38.26 92.47

Muraidih Coalfield– 8.29 11.36 15.73 49.62

Nudkhurkee Western Flank 15.52 17.63 19.29 61.25


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

complete assessment of the effect of coal beneficiation on the wear of

coal rakes. Nevertheless, it can be expected that transportation of

washed coal would extend the life of coal wagons. The cost of a BOBRN

wagon used for coal transportation is Rs. 2 million. A train of 58 wagons

and 5% maintenance spares thus costs about Rs. 122 million or US$ 2.77

million. The life of a wagon is taken as 30 years and its salvage value is

usually reckoned as Rs. 0.25 million. Table 10 shows the savings, which

would appear to accrue, if the life of a wagon were to be extended by

10%, i.e., by three years due to reduced abrasivity of the coal. Using

the straight line depreciation method, the present value of the saving

would be approximately 3% of the capital cost of a wagon, i.e., 3% of

Rs. 2 million ¼ Rs. 60, 000. Thus the total saving for a train of 58 wagons

including 5% maintenance spares would be (61�Rs. 60,000), which is

equal to Rs. 3.66 million or US$ 0.083 million. The savings accruing

due to increase in rake life computed for two other scenarios also appear

to be substantial. As the movement requirement over distances greater

than 500 km is assessed as 276 million tonnes, the implication for savings

in wagon acquisition costs is substantial. Since a rake of 58 wagons costs

about Rs. 122 million, in the maximum and minimum saving scenarios,

life extension of 33 rakes and of 67 rakes would be able to finance the

acquisition of one new rake. Clearly, the impact of lower abrasivity of

coal on the life of a rail wagons is an area where quantitative research

could be very rewarding.

CONCLUSIONS

With a transport elasticity of 1.25 with respect to GDP, transportation

costs will form a significant part of the overall costs of meeting the energy

demand of India. The shear size of the country and location of the coal-

fields make transportation cost one of the major components of thermal

power generation. A generalized 80% yield of washed noncoking coal is

Table 10. Effect of reduced abrasivity on rake life

Savings Rake life extension by

In life (months) 5% (18.0) 7% (25.2) 10% (36.0)

Cost per train

(million Rs.=million US$)

1.825=0.041 2.555=0.058 3.650=0.083


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

likely to provide, on unaltered payload per train basis, a saving in cross-

country transport of 55 Mt, equivalent of 42 trains per day. If IR could

carry only washed power coal, say in 2011–2012, the saving in transport

costs would appear to be sufficient to finance the construction of 467 km

of new track every year. The gross load of the wagon including its own

weight currently in IR cannot exceed 85 tonnes. Preliminary results indi-

cate that, if the load per axle could be increased, because of the reduced

specific gravity of the washed coal, a wagon could carry as much as

85 tonnes of beneficiated coal. It is also expected that transportation

of washed coal, because of reduced abrasiveness, would extend the life of

coal wagons. If the life is extended by 5%, the savings for one coal carry-

ing rake would be Rs. 1.825 million and, if by 10%, the savings would be

Rs. 3.65 million. Therefore, thermal coal beneficiation offers a number of

economic benefits to the coal transporter as well.

REFERENCES

1. Government of India Web site: indianbusiness.nic.in, accessed June 2005.

2. V. K. Singh, Indian Coal Industry–Prospects and Perspective, In Global

Coal, (A.K. Singh and K. Sen, eds.), New Delhi, 2005, pp. 15–28.

3. Draft Report of the Expert Committee on Integrated Energy Policy Document,

Planning Commission, Government of India, December 2005, p. 35.

4. Indian Railway Year Book, New Delhi, 2003–2004.

5. Ministry of Power, Government of India: www.powermin.nic.in, June 2005.

6. Coal India Limited: Annual Reports, Kolkata, 2003–2004.

7. R. K. Sachdev, Cleaning of Thermal Coal–Emerging Indian Scenario, In XIV

International Coal Preparation Congress, Johannesburg, 2002, pp. 489–492.

8. Coal India Limited, June and November 2005, August 2006 (personal

communication).

9. Coal India Limited: Web site, February 2006.

10. Coal India Limited, February 2005 (personal communication).

11. Ministry of Forest and Environment, Government of India, Notification on

Fly Ash dated 19.9.1999.

12. K. K. Sharma, Ash: A Vision, Workshop on, In Characterisation and

Utilisation of Fly Ash, Dhanbad (India), 2005, pp. 6–14.

13. P. Kumar and S. Bhattacharya, Unpublished Research, Indian School of

Mines, 2005.

14. J. J. Wells, F. Wigley, D. J. Foster, W. H. Gibb, and J. Williamson, The

Relationship Between Excluded Mineral Matter and the Abrasion Index of

a Coal, In Fuel, Vol. 83, 2004, pp. 359–364.

15. M. Cresswell, 2006 (personal communication).


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

16. B. Hill, 2006 (personal communication).

17. D. G. Osborne, 2006 (personal communication).

18. J. D. McClung, M. R. Geer, and H. J. Gluskoter, Properties of Coal and Coal

Impurities, In Coal Preparation, 4th ed., (J.W. Leonard, ed.), AIME,

New York, 1979, pp. 1–51.

19. S. N. Mukherjee, Unpublished Research, Indian School of Mines, 2006.

20. Farakka Thermal Power Plant (NTPC), Personal Communication, 2006.

21. S. Bhattacharya, Unpublished Research, Indian School of Mines, 1999.

22. B. Kumar, Effect of Cut-gravity of Washing on Physico-chemical Properties of

Power Grade Coal, M Tech Thesis, Indian School of Mines, 2004.

23. R. Ranjan, Effect of Cut-gravity of Washing on Physico-chemical Properties of

Selected Non-coking Coals, M Tech Thesis, Indian School of Mines, 2006.


Dow

nloa

ded

by [

Uni

vers

ity o

f W

inds

or]

at 2

1:27

25

Sept

embe

r 20

13

impact of coal beneficiation on rail transport in india

Documents