FINAL REPORT

Quantification of Ventilation Air Methane Emission from Gassy Underground Coal Mines in India

Submitted to:

United States Environmental Protection Agency (USEPA) Washington, D.C.

(Program Manager: Dr. Jayne Somers)

Prepared by:

Satya Harpalani Southern Illinois University Carbondale, Illinois, USA

and

Basanta K. Prusty

Central Institute of Mining and Fuel Research, Dhanbad, India

November 2009

TABLE OF CONTENTS

LIST OF FIGURES ……………………………………………………………… iii

LIST OF TABLES ………………………………………………………………. iv

LIST OF ABBREVIATIONS AND UNITS ……………………………………. v

EXECUTIVE SUMMARY ……………………………………………………… vi-vii

1. Introduction and Background ………………………………………………. 1

2. Motivation for Present Study ………………………………………………. 4

3. Objectives ………………………………………………………………….. 5

4. Description of Mines ………………………………………………………. 5

5. Procedures Used …………………………………………………………… 10

6. Results and Analysis ………………………………………………………. 13

7. VAM Quantification ………………………………………………………. 23

8. VAM Utilization Potential ………………………………………………… 26

9. Summary and Conclusions ……………………………………………….. 28

10. Future Work ………………………………………………………………. 29

ACKNOWLWDGEMENTS …………………………………………………… 30

REFERENCES …………………………………………………………………. 31

APPENDIX I Paper, Ninth International Mine Ventilation Congress, New Delhi, India: Quantification of Ventilation Air Methane and its Utilization Potential at Utilization Potential at Moonidih Underground Coal Mine, India ………….… 32 APPENDIX II Methane Concentration Measurements ………………………………………... 42

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LIST OF FIGURES

1. Map of India showing locations of Moonidih and Sudamdih mines …………… 6

2. Typical path of a traverse ………………………………………………………. 12

3. Typical variation of VAM concentration for Moonidih mine – eight hours …… 15

4. Weekly variation of VAM concentration at Moonidih mine – one month .…….. 15

5. Monthly variation of VAM concentration at Moonidih mine – six months …… 16

6. Variation of coal production at Moonidih mine on sampling days …..……….. 16

7. Typical variation of VAM concentration for Sudamdih mine – nine hours …. 20

8. Monthly variation of VAM concentration at Sudamdih mine – six months …. 21

9. Variation of daily coal production at Sudamdih mine on sampling days ……. 21

10. A typical gob showing impact of overlying seams …………………………… 26

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LIST OF TABLES

1. Critical parameters of Moonidih and Sudamdih mines ……………………….. 9

2. Methane profile of Moonidih mine ……………………………………………. 18

3. Q- and c- survey data for Moonidih mine …………………………………….. 19

4. Sealed-off area gas quality at Moonidih mine ………………………………… 19

5. Methane profile of Sudamdih mine …………………………………………… 22

6. Q- and c- survey data for Sudamdih mine ……………………………………. 23

7. Sealed-off area gas quality at Sudamdih mine ……………………..………… 23

8. VAM estimation for Moonidih mine …………………………………………. 24

9. VAM estimation for Sudamdih mine …………………………………………. 26

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LIST OF ABBREVIATIONS AND UNITS VAM: ventilation air methane Q: airflow quantity Q-survey: measurement of airflow quantity c: methane concentration c-survey: measurement of methane concentration MH: meter horizon (term for different levels within the mine) A1, F-3, ML, D-11: names given to different stoppings of sealed off areas, with tappings to collect samples DR: belt loading station X, XI, XII: numbers of the seams E/W: east and west side CO2e: carbon dioxide equivalent v/v: volumetric basis m: meters t: tons Mt: million tons m3/t: cubic meters per ton tpd: tons per day m3/min: cubic meters of airflow per minute Mm3: million cubic meters Tm3: trillion cubic meters Mm3/yr: million cubic meters per year t/yr: tons per year

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EXECUTIVE SUMMARY

Emission of ventilation air methane (VAM) from underground coal mining

operations into atmosphere, although very low in concentration, contributes significantly

to the greenhouse effect responsible for global warming. On the other hand, it represents

a “wasted” resource of immense value. During the last few years, effort has been made to

extract energy from VAM in Australia, US and China using the various technologies

developed to do so from lean methane/air mixture. However, the potential of application

of these technologies has not been assessed for mining operations in India.

The potential of VAM utilization from Indian coal mines is critically dependent

on concentration of methane and its variation over time, given the low coal production

rates from most underground operations. Hence, a preliminary study was undertaken to

assess the VAM resource and its utilization potential at two gassy underground mines in

Jharia Coalfield in India: Moonidih and Sudamdih. These two mines are classified as

Degree III gassy mines according to Indian guidelines, that is, mines with very high gas

emission rate per ton of coal produced.

VAM emission from the two mines studied were measured and characterized in

order to evaluate its utilization potential. A systematic measurement procedure was

carried out over a period of time to measure airflow and methane concentration in the

mine exhaust and various air routes underground. Also, detailed air quantity and methane

concentration surveys were carried out in order to study the characteristics of methane

release from these mines. The measured emission data for a period of six months was

used to calculate the average methane concentration in the exhaust air and analyzed for

consistency of the emissions. A correlation with coal production was established to

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vii

enable dividing the overall emission into two categories, one that is dependent on the

amount of coal produced while the second component that is fixed and independent of

production. Finally, based on measured data, the potential of application of suitable VAM

utilization methods was ascertained.

The results of the study showed that Sudamdih mine does not have any potential

of utilizing VAM at this time due to the extremely low methane concentrations, primarily

due to very low coal production rate. For Moonidih mine, at the current rate of

production, VAM concentration is not high enough to justify its utilization. However, in

the event of increased coal production, currently planned for the near future, there may be

a good potential that the VAM can be utilized to generate electrical power by applying

any of the flow reversal technologies. Also, the hybrid combustion technology that

utilizes both VAM and coal middlings can be applied since the middling can be sourced

from the coal washing plant located close to the mine. The plant would also provide a

market for the energy so produced.

Finally, there were two important findings that were peripheral to the planned

work. First, emission depends on the climatic conditions, the rate being higher during the

summer months. Second, the concentration of methane in sealed off areas of the mine is

very high, varying between 60 and 100%. Also, this concentration varies over time, that

is, these areas “breathe”. This suggests that there is leakage of methane from the sealed

off areas into the mine, resulting in decreased concentration in the areas but increase in

VAM concentration. It also suggests that there is influx of methane from other sources,

like other coal seams in the vicinity since this area of Jharia coalfield has multiple seams,

as many as thirty in some locations.

1. INTRODUCTION AND BACKGROUND

Coal Mining in India

Coal mining industry in India is growing at a rapid state in order to keep up with

the energy needs of the country. The annual coal production was 493 million tons (Mt) in

2008-09. The surface mining operations account for approximately 85% share of the total

coal production. Although the share of underground mines has gradually decreased over

the last three decades, it has stabilized at 15%, and is expected to increase because of

increased focus of Coal India Limited, the major coal producer in the country, on

underground mining. However, increased coal production from underground mines, will

require effective and efficient management of increasing methane emissions from deeper

coals while optimizing the cost of circulating increasing quantities of fresh air in order to

fulfill the ventilation and safety requirements as well as maintain proper working

conditions underground.

Methane Emission from Underground Coal Mines

Coal is a storehouse of natural gas consisting of methane, CO2 and other

hydrocarbons. Methane constitutes more than 80% of the total gas present in coal. The

methane-rich gas is released into the mine workings in underground coal mines posing a

serious risk of explosions. To prevent this, large volume of air is circulated in

underground coal mines by fans, which dilute the methane-rich air and discharge it to

atmosphere. An outcome of atmospheric methane is the resulting greenhouse effect since

methane is twenty times more damaging than carbon dioxide, the number one greenhouse

gas. Atmospheric methane emissions from Indian coal mining and handling activities for

the year 2000 was estimated to be 0.72 Mt using the methodology developed by the

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Central Institute of Mining and Fuel Research (CIMFR) (CMRI, 2003). Quantification of

emissions for the last few years is not available. If International Panel for Climate

Change (IPCC) emission factors are used, the estimated methane emission from Indian

coal mines is estimated to be between 0.54 to 1.69 Mt (Singh et al, 2009). However, at

this time, there is no data available for estimates of methane emission from specific

underground coal mines in India.

As per the Directorate General of Mine Safety (DGMS) in India, underground

coal mines are categorized into three different degrees of gassiness, namely Degree I, II

and III, depending on the volume of gas emitted per ton of coal mined. Degree III mines

typically emit methane at a rate greater than 10 cubic meters per ton (m3/t) of coal mined.

At this time, there are 16 Degree III mines in the country, many of which are located in

the gas-rich Jharia and Eastern Coalfields. According to the CIMFR study (2003), the

emission factor during active mining stage of a typical Degree III mine is 23.6 m3/t,

significantly higher than that from Degree II and I mines, for which the corresponding

factors are 13.1 and 2.9 m3/t respectively.

Ventilation Air Methane

The mine air coming out mine via the exhaust shaft and discharging into

atmosphere contains methane in very small concentrations, typically less than 0.7%. The

methane present in this ventilation air is known as the ventilation air methane (VAM).

Although the concentration of VAM is very small, considering the large volume of mine

ventilation air, it contributes to atmospheric methane emission in a significant way. The

worldwide VAM constitutes about 75% of the total greenhouse gas (GHG) emission from

coal mining activity (USEPA, 2003). In line with the statistics worldwide, it is expected

2

that contribution of VAM towards atmospheric methane from Indian coal mines is

probably high although the exact contribution is not known. Also, VAM emission data

for individual mines are not available since no VAM assessment and utilization studies

have been undertaken to date

VAM Utilization

Utilization of VAM for generation of energy and a means of methane destruction

has been considered as an option for the last several years. The technologies developed

not only abate emission of a potent greenhouse gas, but also generate a value added

benefit from wasted resource in the form of usable energy. However, utilization of VAM

is challenging because of low and varying concentrations of methane in the mine air. The

large quantities of mine exhaust air typically encountered also offer engineering

challenges in the design of systems that are economical and do not hamper the efficiency

of the mine ventilation system. The main commercial barrier to utilization of VAM is that

the mine would probably not be interested in implementing such a system unless it is well

demonstrated to be profitable/beneficial. This is particularly true for Indian conditions,

where underground coal production is low and mines struggle continuously to improve

their productivity.

The various techniques for utilization of VAM generally use the principle of

thermal oxidation or catalytic oxidation of methane to produce heat, which is then used as

a source of useful energy. The technologies for utilization of VAM are classified into

three broad categories: 1) ancillary use technology, 2) principal use technology, and 3)

other technology. A brief description of these techniques is given elsewhere (Srivastava

and Harpalani; 2006, Somers, 2008)

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2. MOTIVATION FOR THE PRESENT STUDY

VAM utilization technologies have been successfully demonstrated at mine sites

in other countries. A growing number of mines are adopting these to generate energy

from utilizing VAM or earn carbon credits. However, to date, there has been no effort in

India to utilize VAM in spite of the obvious advantages of reduction in greenhouse gas

emission as well as generation of a part of mine’s energy requirement. Moreover, India

being a non-Annex I country, the reduction of greenhouse gas emission would also be

eligible for carbon credits thus resulting in generation of additional revenues by utilizing

the VAM. One of the primary reasons for this absence of any VAM utilization projects in

India is the lack of demonstrated technical and economic feasibility of such projects at

specific sites. Successful demonstration of VAM utilization at any Indian mine site(s)

would give mine operators the confidence that such projects are, in fact, viable under

Indian conditions.

At the time this study was initiated, there was no real time VAM emission data

available for Indian coal mines. Hence, the study completed and reported here was

funded by the Methane to Market (M2M) Partnership program of the United States

Environmental Protection Agency (USEPA) as a pre-feasibility study to quantify the

methane emissions into atmosphere from a gassy underground coal mine in India. In

order to select the mines to serve as the best sites for case studies, a preliminary literature

review was carried out to evaluate the gassiness of suitable candidates for the study. After

a preliminary evaluation, Moonidih mine in Jharia coalfield and Chinakuri mine in

Raniganj coalfield were selected for the study. However, during the course of the study,

Chinakuri mine was placed on stand-by status due to some production problem and an

4

alternate mine site had to be identified. Sudamdih mine, also in Jharia coalfield, was

selected as the site for the second case study. Brief description of the two mines is given

in a later section.

3. OBJECTIVES

The specific objective of this study was to quantify the VAM emissions at

Moonidih and Sudamdih mines and conduct a technical pre-feasibility study of VAM

utilization at these mines. The work was aimed at developing a reliable procedure to

quantify the VAM from underground coal mines in India that would work well for future

VAM quantification studies as well. The overall objective was to encourage the

application of this practice at gassy mining operations in India.

4. DESCRIPTION OF THE MINES

Moonidih Mine

Moonidih mine is located in the state of Jharkhand, located sixteen kilometers

from Dhanbad city, well recognized as the coal capital of India. The location of the mine

is shown in Figure 1. With total geological reserves of 1245 million tons (Mt), it is one of

the largest underground coal mines in India. It is also one of the gassiest mines in India,

categorized as Degree III mine. The mine started operation in 1965. The gas content of

the coal seams varies between 6 to 15 m3/t of coal. The mine practices longwall mining

method and is currently mining two faces using shearers. The mine development is

carried out by roadheaders and continuous miners. The actual production is carried out by

longwall retreating method with caving, using powered supports at the face and a single

drum shearer as the coal cutting machine. Although planned for higher capacity, the

5

present production has decreased to less than 1000 ton per day because of the inability of

the mine operator to adopt modern underground mining technology.

Figure 1: Map of India showing locations of Moonidih and Sudamdih mines.

The mine is currently operating at a maximum depth of over 600 m. The annual

coal production is ~ 200,000 tons, which corresponds to an average daily production of

~700 tons. Recently, the mine has entered into a technological collaboration with

Zhengzhou Coal Mining Machinery Company Ltd (ZMG) of China for mining coal from

one of the seams at Moonidih mine. It is expected that with technological assistance from

ZMG, the production from the mine would increase to 700,000 tons annually, that is,

more than 2,000 tons per day. This would mean a three-fold increase in coal production,

if the plans are successful.

The mine has two shafts, both 7.5 m in diameter, one used as intake and the

second as the exhaust shaft. The total quantity of air that is pushed by the main fan to

ventilate the mine is ~12,000 m3/min. The mine is currently operating at three levels,

Moonidih Mine

Jharkhand

Sudamdih Mine

6

known as horizons, namely 280 MH, 400 MH, and 500 MH. Although four seams,

namely XV, XVI, XVII, and XVIII are accessible from the mine, present operation is

restricted to XV and XVI seams only. The XVIII seam has already been extracted. The

coal rank is bituminous, with estimated gas content of 6-15 m3/t of coal. During the very

first visit, one observation was made about the ventilation system. The exhaust shaft has a

rather unusual design with concrete flaps to reduce the air velocity prior to discharging it

to atmosphere. This can be problematic if VAM utilization at the mine becomes a reality.

One of the reasons for selecting Moonidih for this study was the CBM/CMM

demonstration and recovery project in the vicinity. The pilot study, jointly funded by the

Government of India, United Nations Development Projects (UNDP) and Global

Environmental Fund (GEF), was initiated to demonstrate the recovery of coalbed

methane from virgin seams of Moonidih. Methane is currently recovered successfully

from two vertical wells and fed to a generator to produce electricity, which is supplied to

the nearby residential area of the mine. With success of the above study, there is interest

on the part of the mine operator to recover and utilize VAM as well.

Moonidih, being a very old mine, has a large gob area containing large volumes

of mine gas with significant concentration of methane. Recovery of this CMM and

mixing it with VAM may also enable maintain the minimum methane concentration

necessary for VAM utilization. Moreover, the coal washing plant is located less than 250

m from the mine, providing an in-house market for electricity produced by VAM.

Finally, if hybrid combustion technology is found to be suitable, the coal washing plant

can supply the coal middlings, for combustion along with VAM, as a supplement thus

7

increasing the power output from the complete system. However, this study was limited

to quantification of VAM only.

Sudamdih Mine

Sudamdih mine, also located in the state of Jharkhand, was not one of the mines

in the original plan for the current study. However, due to temporary shut-down of

Chinakuri mine, Sudamdih mine was selected as a substitute site for the study.

The mine started in 1962. The geological reserve of the Sudamdih mine is 620

Mt. Although there are more than thirty seams present in the Sudamdih area, the coal

seams encountered in the mine are XV, XI/XII, IX/X, VIIIA and Local seam. Presently,

XI/XII east seam and the eastern part of XV seam are being mined. The western side of

XI/XII seam, VIIIA seam, Local seam and IX/X seam are sealed off. The coal seams in

the mine are thick and steeply dipping (28 to 450) and consist of low angle faults, dykes

and joints. The mine is gassy, with a history of gas explosion in 1976 in XV seam on the

west side, a mine fire in 1977 in XV seam, and again in IX/X seam. The gas content of

the seams was measured to vary between 5 to 15 m3/t of coal. Because of its high

methane emission, Sudamdih is also categorized as a Degree III gassy mine.

Development of the seams has been carried out using the concept of horizon

mining. Three main cross-cuts are driven across all the seams at a depth of 200, 300 and

400 m. From these cross-cuts, galleries are driven along coal seams, which are called

laterals. Each seam has three laterals at 200 m, 300 m and 400 m horizons. Longwall

blocks are formed between horizons 200/300 and 300/400 m and extraction of the blocks

is carried out by a rather unique technique called the Jankowice method. This is a

combination of inclined slicing and hydraulic sand stowing, and extraction is carried out

8

in ascending order. The maximum depth of the mine is 440 m. Typical average

production from the mine is approximately 250 tons per day (tpd) although this has

recently decreased further to 100-150 tpd. The total quantity of ventilation air pumped in

to the mine is approximately 7,000 m3/min. The mine has two ventilation shafts, one

downcast and the second upcast, and one axial fan. Details of the mine, along with those

for Moonidih mine, are presented in Table 1.

Table 1: Critical parameters of Moonidih and Sudamdih mines.

Mine

Parameter

Moonidih

Sudamdih

Location Jharkhand, India Jharkhand, India

Degree of Gassiness III III

Reserves, Mt 1245 620

Estimated Gas Content, m3/t 6 - 15 5 - 15

Depth, m (maximum) 600 440

Coal Production, tpd 700 150

Mining Method Longwall Longwall (Jankowice Method)

Development Cont. Miner Horizon Mining

No. of Shafts Two Two

No. of Fans Two (one standby) One

Airflow, m3/min 12,000 7,000

Working Levels, m 250, 400, 500

200, 300, 400

9

One of the reasons for selecting Sudamdih mine was the high gas content of the

coal seams being mined. One coal mine methane (CMM) demonstration and recovery

pilot project, jointly funded by the Government of India, UNDP and GEF was underway

in the working seams of Sudamdih mine at the time of the study. There was also a

previous project where CMM was successfully recovered from the underground

operation using horizontal boreholes and used to power mine trucks operating in a nearby

surface mining operation. With success of the above study, there was interest on the part

of the mine operator to recover and utilize VAM. Like Moonidih, the Sudamdih coal

washing plant is located ~ 250 m from the mine thus providing an ideal market for the

energy generated from VAM. It is worth mentioning that the underground drilling for

CMM recovery was abandoned earlier in 2009 due to difficult drilling conditions.

5. WORK PROCEDURE

As a first step, mine plans were secured from the mine operators and studied to

determine the methane monitoring locations. These locations included all exhaust routes,

working faces, main intakes and return, and development areas. The route for the mine-

wide methane survey was planned and discussed with the mine personnel. This was

followed by carrying out a mine-wide methane emission survey, as described by

McPherson (1993) and summarized below. The survey included airflow measurements

(Q-survey) throughout the mine, and measurement of methane concentration (c-survey)

at every Q-station. Using the Q and c measurements, the amount of methane content of

air was calculated at each location.

For Q measurement, a vane anemometer and a stopwatch were used. The

anemometer measures the length of air that passes through it over a period of time. The

10

continuous traverse technique was used since this gives an average velocity of airflow

passing through a vertical plane over the entire cross-section. The anemometer was

attached to a 1.5 m long rod to ensure that the person taking the measurement did not

change the velocity profile. The attachment also allowed anemometer to hang vertically

at all times. The anemometer was held in the lower corner of the airway, as shown in

Figure 2, with pointer set to zero. The observer then reached forward to touch the control

lever while the second observer with a stopwatch counted backwards from five to zero.

On count of zero, the control lever was pressed, activating the measurement of flow. The

entire airway cross-section was traversed in sixty seconds, covering approximately equal

areas in equal time divisions. At fifty-five seconds, the observer with the stopwatch

counted to sixty, at which instant, the control was pressed again. The anemometer reading

gave the length of air that passed through it in sixty seconds, providing the velocity in

meters per minute. Two readings were taken at every station.

For measurement of gas concentration, a capsule (tube) filled with water was used

at the measuring station. Again, the entire cross-section of the airway was traversed over

a one-minute period. During the traverse, water was displaced by air over the cross-

section. At the end of the traverse, air in the capsule was locked using clamps (that came

with the capsule) and the capsule was labeled. It was then placed in a cooler. Once on the

surface, the air was analyzed for composition. At every station, a hand held

methanometer (Solaris, Mine Safety Appliances) was also used for spot measurement.

However, at stations with high air velocities, there was significant fluctuation in the

methanometer readings. The methanometer is a useful instrument for quick checks but

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the readings are given only to one decimal place. For VAM estimation, gas analyzer

gives more accurate compositional information.

Figure 2: Path of a traverse (McPherson, 1993).

A thorough and rigorous technique was followed to assess the VAM emission

from the mine. Air samples were collected from the main return of the mine and analyzed

for methane concentration. For a six-month period, one measurement was taken every

month, on a working day with full production. For one of the months, methane

concentration was measured every week. For one of the weeks, the measurement was

carried out every day, and for one of the days, the measurement was carried out every one

hour. For one of the days, readings were taken every fifteen minutes over a six-hour

period. Hence, a complete array of methane emission data was obtained during the study

period. The measurements were taken in the mine exhaust system since this is the

primary route for methane escape. The detailed measurements were used to calculate the

12

annual emission as well as daily emission rate and thus provided the overall emission rate

from the mine. Finally, the VAM emission results were correlated with coal production

data for the various periods in order to estimate the emission that is independent of

production, and that directly related to coal production. In other words, on an idle day

with no coal production, there is still some methane entering the exhaust air. The primary

source of this methane is exposed coal surface, where methane continues to diffuse for

long period of times after mining, and from coals above and below the working seam.

This aspect of the study was particularly critical for Moonidih mine since coal production

is expected to increase significantly in the near future thus resulting in a significant

change in the methane emission patterns. The component of the overall emission that is

expected to go up is that depending on the amount of coal mined.

6. RESULTS AND ANALYSIS

Moonidih Mine

The PIs met with the mine personnel in July 2007 and discussed the scope of the

study and detailed plans for the study. Mine personnel was very supportive of the study.

The Mine Ventilation Engineer and Mine Project Engineer were identified as the points

of contact for all future plans. The major part of the study was carried out during the

period December 2007 to May 2008. Exhaust air samples were collected from the

exhaust shaft of the mine. The hourly and daily samples were collected during the week,

December 11 to 14, 2007. The weekly samples, that is, hourly sampling on one day

every week of the month was carried out during the months of December 2007 and

January 2008. The monthly samples, that is, hourly sample for one day of every month,

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were collected through May 2008. The coal production data was also collected for each

day of air sampling.

The air samples were analyzed using a Riken Keiki HC analyzer (Model No. RI

415) within a few hours after collection. The Riken Keiki HC analyzer detects methane

with a non-dispersive infrared sensor with an accuracy better than ±5%, with capability to

detect and accurately measure methane concentration ranging from very low

concentrations (< 0.054%) to pure methane (100%).

In order to estimate the dependence and correlation between the concentration of

VAM and daily coal production, exhaust samples were also collected on one idle day,

when there was no coal production. The variation of methane concentration on a

producing day and an idle day are shown in Figure 3. The upper plot shows the VAM

concentration on a coal production day, when 510 tons of coal was produced. The lower

plot shows the variation of VAM concentration on an idle day. It is apparent that the

methane concentration on the idle day was fairly constant and remained at 0.10% level.

This is, therefore, also the minimum concentration on a producing day. On the production

day, the maximum concentration of VAM was measured to be ~0.20%.

The methane concentration of the hourly samples collected was averaged and

daily average values were obtained. The average VAM concentrations for the sampling

day of successive weeks between December 11, 2007 and January 2, 2008 are shown in

Figure 4. Similarly, average VAM concentrations for the sampling days of successive

months between December 2007 and May 2008 are shown in Figure 5. Figure 6 shows

the daily coal production on the days when sampling was carried out. The variation is

14

between 485 and 800 tons, which is not a significant range although the relative

difference is significant.

0.00

0.05

0.10

0.15

0.20

10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00

Time, hh:mm

Met

han

e C

once

ntr

atio

n, %

.

.

Working

Idle

Figure 3: Typical variation of VAM concentration for Moonidih mine – eight hours.

0.00

0.05

0.10

0.15

0.20

1 2 3 4

Week

Met

han

e C

once

ntr

atio

n, %

.

Figure 4: Weekly variation of VAM concentration at Moonidih mine – one month.

15

0.00

0.05

0.10

0.15

0.20

Dec Jan Feb Mar Apr May

Month

Met

han

e C

once

ntr

atio

n, %

.

Figure 5: Monthly variation of VAM concentration at Moonidih mine – six-months.

0

200

400

600

800

1000

Dec Jan Feb March Apr May

Month

Pro

du

ctio

n, t

onn

es/d

ay

.

Figure 6: Variation of coal production at Moonidih mine on sampling days.

16

The average methane concentration varied between 0.13 and 0.20%, which is a

fairly narrow range. The coal production on sampling days is relatively narrow as well. It

is interesting to note that although coal production during the summer months, that is,

April and May, 2008 was less than in winter months of December, 2007 and January,

2008, the average VAM concentrations were higher during the summer months. One

possible reason for this could be the higher air temperature during the summer months,

compared to the winter months. Although the temperature of the mine air was not

measured, it can be assumed with fair certainty that the mine air temperature during

summer would typically be higher than that in the winter months, since artificial cooling

and heating of the mine air is not practiced. The average temperature (ambient) during

the month of May is 330C, whereas in December, it is 200C. A difference of 130C is

significant, warranting higher rate of desorption and diffusion of methane from coal

during summer and thus resulting in a higher concentration of methane in mine air. It is

worth mentioning that this is based on single day measurements.

Air quantity and quality surveys (Q and c survey) were carried out across the

mine between December 11 and 14, 2007, covering all working faces, including the

development areas, district return and main returns of the mine. Air quantity was

calculated by measuring the cross sectional area of the mine roadway and the average air

velocity across the section at the measuring stations. The product of the two gives the

volumetric flowrate (m3/min). Air samples were collected from several locations

including the Q-survey stations to estimate the methane content of air. The survey data is

presented in Tables 2 and 3. The data presented in Table 2 indicates that the methane

concentration in the mine at different locations varied between 0.1 to slightly more than

17

0.2 %. Only in the longwall panel return entry was the methane concentration higher on

one of the survey days.

Additionally, samples were collected from some of the sealed off areas of the

mine and methane concentration for each sample was measured although this was not a

part of the proposed study. Since Moonidih is a very old mine, there are approximately

seventy sealed off areas in Moonidih mine and some of the sealed off areas showed very

high concentrations of methane. The results of the gas quality data in the sealed off areas

is shown in Table 4. It can be seen that the methane variation was between 60 and 100

%. Also, measurements on two different days showed that these areas “breathe”, that is,

the methane concentration changes over time.

Table 2: Methane profile of Moonidih mine.

No. Sample Location Sampling DateMethane

Concentration (%)

1 DR belt dip junction (with returns) 11.12.2007 0.11

2 DR belt dip junction (blind heading) 11.12.2007 0.13

3 Longwall panel return (down) 11.12.2007 0.22

4 15 seam working district (active) 12.12.2007 0.11

5 Development face 14.12.2007 0.11

18

Table 3: Q- and c-survey data for Moonidih mine.

No. Sample Location Sampling Date Air quantity

(m3/min)

Methane Concentration

(%)

1 DR belt dip junction (blind heading) 11.12.2007 232 0.13

2 Longwall return top gate 11.12.2007 554 0.22

3 500 L return (part return) 12.12.2007 3482 0.12

Table 4: Sealed-off area gas quality at Moonidih mine.

No. Sample Location Sampling Date Methane

Concentration (%)

1 F-3A top gate stopping 13.12.2007 60

2 A1 – S/G XVIII seam stopping at 400 MH 13.12.2007 100

3 ML – 1/6T gate stopping, 400 MH 13.12.2007 50

4 D-11 salvage gallery stopping 13.12.2007 60

Sudamdih Mine

The study for the Sudamdih mine was conducted during the months of April and

August, 2008. Exhaust air samples were collected from the exhaust shaft of the mine. The

weekly samples, that is, hourly sampling on one day, every week of the month, were

collected during the months of April and May, 2008. The monthly samples, that is, hourly

sample in one day of one month, were collected between April and August of 2008. The

coal production data was also collected for each sampling day. The exhaust samples were

analyzed within a few hours after collection.

In order to estimate the dependence of methane concentration on daily coal

production, exhaust samples were also collected on an idle day, when there was no coal

19

production. Hourly variation of VAM concentration on a typical producing day is shown

in Figure 7. The variation in concentration of VAM on an idle day is also shown in the

same figure. It is apparent that the concentration of VAM is very low, varying between

0.02 to 0.04 % on a producing day. On an idle day, the VAM concentration is constant at

0.02%. The variation of daily average VAM concentration values on the days sampled in

successive months (March to August 2008) is shown in Figure 8. The average VAM

concentration varied between 0.02 to 0.03%. These are very low levels of methane

concentration from any VAM utilization perspective. Hence, it was apparent that this

mine had no potential for any VAM project although such low concentration of VAM is

not surprising given the poor daily coal production at the mine. The coal production from

the mine on sampling days during different months is shown in Figure 9. It is apparent

that typical production of the mine is just above 100 tons, which is really low.

0.00

0.01

0.02

0.03

0.04

0.05

7:50 8:50 9:50 10:50 11:50 12:50 13:50 14:50 15:50

Time, hh:mm

Met

han

e C

once

ntr

atio

n, %

.

.

Working

Idle

Figure 7: Typical variation of VAM concentration for Sudamdih mine – nine hours.

20

0.00

0.01

0.02

0.03

0.04

Mar Apr May Jun Jul Aug

Month

Met

han

e C

once

ntr

atio

n, %

.

Figure 8: Monthly variation of VAM concentration at Sudamdih mine – six months.

0

30

60

90

120

150

Mar Apr May Jun Jul Aug

Month

Pro

du

ctio

n, t

onn

es/d

ay

.

Figure 9: Variation of daily coal production at Sudamdih mine on sampling days.

21

Q- and c-surveys were carried out covering all the working areas, district return

and main returns of the mine to ascertain methane profile of the mine. The survey

consisted of measurement of air quantity and collection of mine air samples for

measuring the methane concentration. In addition to these, few samples were also

collected from inside the mine stoppings to obtain qualitative information about the gas

content of the sealed off areas of the mine. The survey was carried out between August

13 and 21, 2008. The survey results are shown in Tables 5 and 6 respectively.

The results showed that methane concentration in the mine air is also very low,

varying between 0.01 to 0.03%. Sealed off gas quality data presented in Table 7 shows

that, unlike Moonidih mine, gas is not very rich in methane. Overall, the methane profile

and VAM concentration profile for Sudamdih mine is not very encouraging for any VAM

utilization at this point in time. Also, it appears unlikely, based on meetings with the mine

personnel, that coal production from the mine is going to improve in any significant way

in the future. Hence, this part of the study can be considered a “failed” effort.

Table 5: Methane profile of Sudamdih mine.

No. Sample Location Sampling

Date

Methane Concentration

(%)

1 XI/XII E 5 dip at 300- 400 MH 13.08.2008 0.03

2 XI/XII E 7 dip at 300- 400 MH 13.08.2008 0.02

3 XI/XII E 6 dip at 300- 400 MH 13.08.2008 0.02

4 Return shaft no. 2 at 400 MH 13.08.2008 0.03

5 200 MH XI/XII district 21.08.2008 0.02

6 200/300 MH, 4-5 block, XI/XII East 21.08.2008 0.01

7 200 MH XI/XII E 7 dip 21.08.2008 0.02

22

Table 6: Q- and c-survey data of Sudamdih mine.

No. Sample Location Sampling

Date

Air Quantity(m3/min)

Methane Concentration

(%)

1 XI/XII East 5th dip 300-400 MH 13.08.2008 252 0.03

2 200 MH XI/XII district return 21.08.2008 2380 0.02

3 XI/XII East 200-300 MH, 4-5 block 21.08.2008 1146 0.01

Table 7: Sealed-off area gas quality at Sudamdih mine.

No. Sample Location Sampling Date CH4

Concentration (%)

1 200 MH, N cross cut 21.08.2008 17%

2 200 MH, XI/XII W 21.08.2008 20%

7. VAM QUANTIFICATION

Moonidih Mine

The results presented in Figure 3 show that the range of variation in methane

concentration with no coal production through ~500 tons per day production is between

0.1 and 0.2 %. The total methane emission at the current rate of emission was calculated.

The results are shown in Table 8. The range of annual VAM emission was calculated to

be 6.3-12.6 Mm3. The mean VAM estimate was estimated to be 6342 t per year. With

coal production increasing to 2,100 tpd, the amount of methane emitted would vary in the

range of 6.3-31.6 Mm3 (last column in Table 8), depending on idle versus full-production

time. There are two assumptions in these calculations. First, the increase in VAM

concentration with production is linear at the rate of 0.1% per 500 ton of coal (obtained

23

from Figure 3). This is a reasonable assumption since the amount of methane released

from fresh coal mined is a function of production. Second, the future daily production of

2,100 tons is actually achieved, indeed a serious assumption. Furthermore, the airflow

into the mine is not increased due to increased coal production. This is also a reasonable

assumption since the overall current airflow for the mine is adequate even for increased

production. It is the optimum distribution of airflow throughout the mine that has

presented a challenge at this mine. The VAM concentration for a 2,100 ton daily

production is thus estimated to be 0.5%, an encouraging finding at the mine.

Table 8: VAM estimation for Moonidih mine.

Production

Details Current Daily Production (~700 tons)

Increased Daily production (~2100 tons)

Air quantity, m3/min 12,000 12,000

Air discharged in one day, Mm3 17.28 17.28

Air discharged in one year, Tm3 6.3 6.3

VAM emitted @ 0.1% (v/v), Mm3/yr 6.3 6.3

VAM emitted (v/v), Mm3/yr 12.6 (0.2%) 31.6 (0.5%)

Mean VAM estimate per year, Mm3 9.4 18.9

Mean VAM estimate per year, t 6,342 12,683

Methane destruction by TFRR, t/yr 6,024 (95%) 12,049

CO2 equivalent emission reduction, t/yr 10,9947 219,893

Carbon credits @ $10/ton, $/yr 1.10 M 2.20 M

24

The minimum VAM concentration is also expected to increase from the present

level of 0.1% due to increased working area due to the amount of coal exposed as a result

of increased production. In the US, a significant amount of methane encountered in

longwall operations originates from coals above and below the working horizons. This

component of methane influx is a direct function of the rate of face advance, which

influences the rate of advance of the gob. Methane influx is particularly significant in

mines that have several coal seams above and below the working seam. A typical

example of a longwall operation with other seams in the vicinity is shown in Figure 10.

At the Moonidih mine, there are several seams above and below the working seam and

this component is, therefore, expected to be significant. An indication of this is the high

concentration of methane in the sealed off areas and the fact that the concentration

changes over time suggesting these areas are “breathing”. Typically, this is indicative of

continuous methane influx from nearby seams. It is, therefore, possible that the

concentration level on idle days would increase to 0.2% or more, which is the lower cut-

off required for application of any flow reversal technique. Thus the principal VAM

technology, that is, flow reversal technology, may become viable to produce energy.

Sudamdih Mine

The range of variation of VAM concentration with no coal production through

~120 tons production is between 0.02-0.04 percent (Figures 7 and 8). The total VAM

emission at the current rate of emission was calculated and is presented in Table 9. The

range of annual VAM emission was calculated to be 0.74-1.48 Mm3. The mean VAM

estimate was calculated to be 740 t per year.

25

Figure 10: A typical gob showing impact of overlying seams (Hartman, 1997).

Table 9: VAM estimation for Sudamdih mine.

Details Values

Air quantity 7,000 m3/min

Air discharged in one day 10.08 Mm3

Air discharged in one year 3.68 Tm3

VAM emitted @ 0.02% (v/v) 0.74 Mm3

VAM emitted @0.04% (v/v) 1.48 Mm3

Mean VAM emission estimate per year 1.1 Mm3

Mean VAM estimate emission per year 740 t

8. VAM UTILIZATION POTENTIAL

Moonidih mine

Any successful VAM utilization alternative would prevent the emission of 9.4

Mm3 of methane in one year at the current rate of coal production, assuming 100%

capture. The emitted VAM is, therefore, a significant quantity. However, the current

emission rates of VAM are too low for application of the principal VAM utilization

26

techniques, which typically require a minimum of 0.2% methane concentration or more at

all times. Some of the ancillary use technologies may possibly be used. Application of the

Australian Hybrid coal/methane combustion technology appears to be promising because

of the presence of the coal washing plant near the mine. The plant middlings may be

burnt in a rotary kiln using the mine return air containing VAM as part of the combustion

air although the economic feasibility of this alternative needs to be worked out.

In the scenario of 2,100 tpd at the Moonidih mine, the principal use technologies,

such as TFRR/VAMOX, can be applied. However, at many of the mines where TFRR

system has been installed, energy has been recovered as heat and used for heating water

and air, etc., at the mine site. In India, such use of heat is not required at this time. This is

particularly true for Moonidih mine since there is no hot water or air at the mine facility.

Hence, recovering energy from VAM at the present does not appear to be an attractive

alternative. However, use of thermal energy for coal washing/drying is a possibility

although such use of energy would depend on the economics of such an operation. Also,

installation of TFRR for destruction of VAM may be practiced. With >95% efficiency,

the TFRR system would successfully destroy 12,049 tons of methane per year. This is

equivalent to reduction of 219,893 tons of CO2 equivalent emission and would qualify

for carbon credit revenue of ~$2.20 Million per year, assuming $10 per equivalent ton of

CO2 emission. With 50% capture, this translates to more than 6,000 tons of methane,

~110,000 t of CO2 equivalent emission, resulting in ~$1.1 Million. At this time, this

appears far-fetched, given the prevailing conditions at the mine, but real.

27

Sudamdih mine

At this time, the range of variation of VAM is between 0.02 and 0.04%, which is

very low for application of any of the VAM utilization technique. Hence, there is no

potential of utilization of VAM at Sudamdih mine. The concentration of VAM may be

increased to the lower limit of application of flow reversal technique only when the coal

production increases by several times the current production. However, Sudamdih mine

is a technically challenging mine due to the steepness of the coal seams and presence of

faults. The mine operator is looking for technology transfer from overseas to enhance the

production and productivity. The situation may be revisited only after multifold increase

in coal production. Based on the visits by PIs, this is unlikely to happen in the foreseeable

future. Hence, the PIs believe that the idea of VAM utilization at Sudamdih mine should

not be pursued at this time.

9. SUMMARY AND CONCLUSION

A systematic and detailed study was taken up at Moonidih and Sudamdih mines,

both in the Jharia coalfields of India, to quantify the emission of VAM and assess the

potential for use of any VAM utilization technologies. The study at Moonidih mine

demonstrated that a large quantity of VAM, an average 6,342 tons, is emitted from the

mine every year. However, methane concentration varies between 0.1 to a maximum of

0.2 %. Since the minimum methane concentration is 0.1%, there is no suitable principal

use technology available to utilize the large amount of VAM. The applicability of

ancillary use technology, such as the Australian Hybrid technology, can be considered for

its economic feasibility. The lower concentration of VAM at the mine is primarily due to

the low daily production of coal, and it is expected that, with acquisition of technology

28

from China in the near future, coal production form the mine will increase substantially.

If this plan materializes, the principal use technology may become applicable. With

installation of the TFRR system, there is potential to earn carbon credits worth $1-2

M/year.

The study at Sudamdih mine suggested that approximately 740 t of VAM is

emitted from the mine every year. However, the VAM concentration being extremely low

(0.02-0.04%), none of the VAM utilization techniques can be applied now. In the

scenario of significant increase in coal production in the future, although this appears

extremely unlikely at this time, the study may be repeated to evaluate VAM utilization

potential at the mine.

10. FUTURE WORK

It is apparent that the real potential at Moonidih mine is utilization of VAM when

the current plan to increase the coal production materializes. At that time, a second

assessment study can be carried out to re-evaluate the situation. At this time, there is

obvious potential of recovering methane from sealed off areas. The mine is old and has a

large number of sealed off areas with high concentration of methane. These areas also

“breathe”, that is, the methane concentration varies over time, which is a positive finding.

Hence, a systematic study should be undertaken to assess the amount of methane in these

areas and evaluate the various alternatives available to capture the gas.

29

ACKNOWLEDGEMENTS

This work was performed with funding from the US Environmental Protection

Agency’s Methane to Market Partnership. The authors and the two organizations,

Southern Illinois University Carbondale and Central Institute of Mining and Fuel

Research, express their gratitude for the support provided by US EPA. The authors wish

to thank Dr. Jayne Somers, the EPA Program Manager for this study, for the support and

constant guidance that she provided. Finally, the authors wish to thank Drs. A.K. Singh

and A. Sinha of CIMFR for their support throughout the duration of the study.

30

REFERENCES CMRI, 2003, Uncertainty Reductions in Greenhouse Gas Inventories Associated to Coal

Mining, Project report prepared as part of India’s Initial National Communication Project executed by Ministry of Environment and Forests, Government of India.

McPherson, M. J., 1993, Subsurface Ventilation and Environmental Engineering, Chapman & Hall, London.

Singh, A.K., Sahu, J.N. and Meikap, B. C., 2009 (in Press), Coal Mine Gas Uses for Hazardous Waste Management in India, International Journal of Environment and Waste Management.

Srivastava, M. and Harpalani, S., 2006, Systematic Quantification of Ventilation Air methane and its Evaluation as an Energy Source, Mining Engineering, Vol. 58, No. 11, Nov., pp. 52-56.

USEPA, 2003, “Assessment of the Worldwide Market Potential for oxidizing Coal Mine Ventilation Air Methane”, EPA-430-R-03-002.

Somers, J., 2008, “Global CMM Emissions and Activities”, presentation at the India Coal Mine/Coalbed Methane Clearinghouse, Kick-off Event, November 17-18, Ranchi, India.

Hartman, H.L., Mine Ventilation and Air Conditioning, ed. John Wiley and Sons, 1997, pp 68.

31

32

APPENDIX I

Paper, Ninth International Mine Ventilation Congress, New Delhi, India: Quantification of Ventilation Air Methane and its Utilization Potential at Moonidih Underground Coal Mine, India

QUANTIFICATION OF VENTILATION AIR METHANE AND ITS UTILIZATION POTENTIAL AT MOONIDIH UNDERGROUND COAL MINE,

INDIA

B. K. Prusty1, S. Harpalani2 and A.K. Singh3

1 Assistant Professor, Mining Engineering Department, Indian Institute of Technology, Kharagpur - 721 302, India

Email: bkprusty@mining.iitkgp.ernet.in. 2 Professor and Chair, Department of Mining and Mineral Resources Engineering, Southern Illinois

University Carbondale, IL 62901, USA Email: satya@engr.siu.edu

3 Scientist, Methane Emission and Degasification Division, Central Institute of Mining and Fuel Research, Barwa Road, Dhanbad – 826 015, India

Email: ajayabha@yahoo.com

ABSTRACT

Emission of ventilation air methane (VAM) from underground coal mining operations into atmosphere contributes significantly to the greenhouse effect. On the other hand, it also represents a “wasted” valuable resource. In recent years, effort has been made to extract the energy from this lean methane/air mixture using combustion/utilization technologies developed and tried in mining operations in Australia, US and China. However, utilization of VAM is technically feasible only when the VAM volume is substantial, methane concentration is relatively constant and above a threshold value. This paper describes a preliminary study undertaken to assess the VAM resource and its utilization potential at Moonidih underground mine in India. Methane emission and daily coal production at the mine made it ideally suited for the study. A systematic airflow and methane concentration measurement in the mine exhaust was carried out over a period of time. Also, a detailed survey was carried out in order to study the characteristics of methane release within the mine. The measured emission data was used to calculate the average methane concentration in the exhaust air and analyzed for consistency of methane emissions with, and without, coal production. Using projected coal production from the mine, future VAM emission was predicted. Finally, based on data collected, a comparison was carried out to identify applicable methods of VAM utilization. KEYWORDS: COAL MINING, VENTILATION AIR, METHANE, VAM UTILIZATION

1. INTRODUCTION AND BACKGROUND Coal mining industry in India is growing at a rapid pace to keep up with the energy needs of the country. The annual coal production was 463 million tons (MT) in the year 2007-08 and the target production for the year 2008-09 is 497 MT. The opencast mines account for approximately 85% share of the total coal production. Although the share of underground mining has gradually decreased over the last three decades, it has now stabilized at 15%. It is expected to increase because of enhanced focus of Coal India Limited, the major coal producer in the country, to produce more coal. Increased production of coal from underground mines, however, will require efficient management of methane emission from deeper coals while optimizing the cost of circulating increased airflow in order to fulfill the ventilation and safety requirements.

33

1.1 Methane emission from underground coal mines Coal serves as a storehouse of natural gas consisting primarily of methane, CO2 and other hydrocarbons. Methane constitutes more than 80% of the total gas present in coal. The methane rich gas is released into the mine workings of underground mines causing increased risk of explosions. To prevent such explosions, sufficient volume of air is circulated in the mine to ensure dilution of methane and its discharge to atmosphere. Atmospheric methane, being a stronger greenhouse gas, abets the global warming significantly. Methane emission into atmosphere from Indian coal mining and handling activities for the year 2000 was estimated to be 0.72 MT using CIMFR methodology (CMRI, 2003). If IPCC emission factors are used, the estimate is between 0.54 to 1.69 MT (Singh et al, 2009). However, at this time, there is no data available for estimates of methane emission from specific underground coal mines in India. As per the Directorate General of Mines Safety (DGMS) in India classification, underground coal mines in India are categorized into three different degrees of gassiness, namely degree I, II and III, depending on the volume of gas emitted per ton of coal mined. Mines in Degree III typically emit methane at a rate greater than 10 cubic meters per ton of coal mined. At this time, there are 16 degree III mines in the country, many of which are located in the gas-rich Jharia and Raniganj coalfields. According to a CMRI study (2003), the emission factor during active mining stage of a typical degree III gassy mine is 23.64 (m3/t), significantly higher than that of a degree II and I mines, which are 13.08 and 2.91 (m3/t) respectively. 1.2 Ventilation air methane The mine air coming out of the exhaust shaft and discharging into atmosphere contains methane at very low concentrations, usually less than 0.75%. Methane present in ventilation air is known as ventilation air methane (VAM). Although the concentration of methane is very small, considering the large volume of VAM, it constitutes a significant addition to the atmosphere. For example, worldwide VAM constitutes about 75% of the total greenhouse gas (GHG) emission from coal mining activity (USEPA, 2003). In line with the world-wide statistics, it is expected that the contribution of VAM towards methane emission from Indian coal mines would also be significnat although the exact share is not known at this time. Also, VAM emission data for individual mines in India is not available. 1.3 VAM utilization The potential of VAM utilization for generation of energy is not a novel idea since it not only abates emission of a potent greenhouse gas but also generates value/energy out of a resource that is otherwise “wasted”. However, utilization of VAM is challenging because of very low, and constantly changing concentration of methane in air. Furthermore, large quantities of the mine air offer engineering challenges for designing and handling it economically without hampering the efficiency of the ventilation system of the mine. Finally, the main commercial barrier to VAM utilization is the unwillingness of the mine operators to implement such a system unless it is demonstrated to be profitable. Techniques for utilization of VAM generally use principles of thermal oxidation or catalytic oxidation of methane to produce heat, which is then used to produce useful energy. The technologies for utilization of VAM are classified into three broad categories: 1) ancillary use technology, 2) principal use technology, and 3) other technology (Srivastava and Harpalani, 2006). 1.3.1 Ancillary use technology: In a combustion system, oxygen of the ambient air combines with the primary fuel to generate useful energy. Ancillary use technology uses ventilation air instead of the ambient air to provide the needed oxygen for combustion. In this alternative, VAM constitutes only a fraction of the combustion process, and thus, not the entire VAM is utilized while the rest is vented to atmosphere. Ancillary use technologies include (Su et al, 2005):

Hybrid coal/methane combustion units, and

Internal combustion engines.

34

Hybrid coal/methane combustion units (rotating kiln): A technology developed by CSIRO of Australia uses a rotating kiln, where waste coal is combusted with VAM or mine methane and the kiln’s exhaust gas heats clean air which powers an unfired gas turbine to produce energy. This technology has the flexibility to operate on a wide spectrum of VAM-to-coal ratios and VAM concentrations. The hybrid system can be developed in small to medium size, with capacity varying between 10 to 100 MW (Su et al, 2005). Internal combustion engines: Internal combustion engines commonly use medium quality gas to generate electricity, and are suitable for using part of a ventilation air stream by substituting it for fresh ambient air in the combustion air intake. At Appin Colliery, Australia, 54 one-megawatt Caterpillar G3516 spark-fired engines have been installed to use drainage gas as the primary fuel. At this plant, VAM contributes between 4 and 10% of engine fuel, corresponding to the consumption of approximately 20% of the ventilation emissions (Su et al, 2005). 1.3.2 Principal use technology: In this case, VAM serves as the primary fuel and the combustion system does not rely on any other source of combustion. Major principal use technologies are thermal flow-reversal reactor (TFRR) and catalytic flow-reversal reactor (CFRR). Thermal Flow Reversal Reactors: The TFRR utilises the thermal oxidation principle to generate heat which is then converted to electrical power. VOCSIDIZER, developed by MEGTEC Inc., the most common TFRR system, employs the principle of regenerative heat exchange between a gas (ventilation air) and solid (heat exchange medium selected to store and transfer heat). The VOCSIDIZER is self-sustaining at low methane concentrations (0.2%-1.2%) and requires no other source of fuel (USEPA, 2007). The VOCSIDIZER has the capability to oxidize >96% of VAM. It has been used successfully in mines in the UK, where it treated about 8000 m3/h of ventilation air with methane concentration varying between 0.3 and 0.6 %. Another system has been installed in West Cliff colliery in Australia in 2005 that generates 6 MW of energy using 250,000 m3/h of ventilation air. A second type of thermal oxidizer reactor, namely VAMOX, has been developed by Biothermica that can run on 0.2% methane. The VAMOX oxidizes the VAM into CO2 and water, while the heat produced can be recovered to produce hot water or transferred to generate electricity. The VAMOX has the capability to oxidize 98% of VAM. The VAMOX is currently being tried at Jim Walter Resources' Mine No. 4, in Brookwood, Alabama, USA (USEPA, 2008). Catalytic Flow Reversal Reactor: The CFRR system, developed by Canadian Mineral and Energy Technologies (CANMET), is similar to the TFRR in design and operation. However, the advantage of CFRR is that the ventilation air is oxidized at lower temperatures (350-8000C) by using a catalyst which reduces the auto-ignition temperature of methane by several hundred degrees Celsius (USEPA, 2003). The CFRR system has been demonstrated at a Canadian mine site. 1.3.3 Other technologies: Several lean burn gas turbines have been developed which can use VAM or enriched VAM to produce power (USEPA, 2003). Energy Developments Ltd. (EDL) has developed a recuperative gas turbine that is capable of firing a methane-in-air mixture as low as 1.6 percent. A generator coupled to the power turbine can generate up to 2.7 MW. Ingersoll-Rand of USA has developed a micro-turbine with a catalytic combustor powered with 1% methane in air. FlexEnergy has developed a micro-turbine which is capable of operating on methane concentrations as low as 1.3 percent. A catalytic combustion gas turbine system, VAMCAT, has been designed by CSIRO of Australia which can run on 1% methane. Concentrators can also be used to enrich methane in mine air to make the ventilation air more usable. The concentrator can increase the >0.1 % methane-air to >20% methane stream which can be used in a turbine or engine to generate power (Su et al, 2005).

35

2. MOTIVATION FOR THE PRESENT STUDY VAM utilization technologies have been successfully demonstrated at mine sites in several countries and a growing number of mines are going to generate and utilize the energy from VAM in the future. However, as of today, there has been no effort in India to utilize VAM for generating energy. Moreover, India being a non-Annex I country, the reduction of greenhouse gas emission is eligible for “Carbon Credits” enabling the mine operators to earn revenues by utilizing VAM. One of the reasons for this non-activity in this area in India is the lack of demonstrated technical and economic feasibility of such projects at specific sites. A successful demonstration of VAM utilization in any Indian mines would provide operators the required confidence. Therefore, Methane to Markets (M2M) program was approached to fund a pre-feasibility study of VAM utilization at a prospective mine in India. After analyzing the available data, Moonidih mine in the Jharia coalfield was selected for the study. It is a highly gassy mine with significant coal production and appeared to have good potential for VAM utilization. The objective of the present study was to fill the information gap and establish a VAM emission profile of the mine and propose possible VAM utilization alternatives at the mine. This paper describes the study completed to quantify the VAM emission at Moonidih mine and conduct a technical pre-feasibility study of VAM utilization. The broader objective of the work was to develop the application of this practice to gassy mines with large VAM emissions in India by developing a reliable procedure to quantify the VAM from underground coal mines in India, establish the distribution of methane throughout the mine, and identify the primary sources of emission.

3. DESCRIPTION OF THE MOONIDIH MINE

Moonidih mine is located in the district of Dhanbad in the state of Jharkhand, located sixteen kilometers from the city of Dhanbad The exact location of the mine is shown in Figure 1. With a total geological reserve of 1244.8 MT, it is one of the largest underground coal mines in India. The mine started operation in 1965. It is also one of the

Moonidih Mine

Jharkhand

Figure 1: Map of India showing the location of Moonidih mine

36

gassiest mines in India, falling in degree III category. The mine practices longwall mining method and is currently mining two faces using shearers. The mine is developed by roadheaders and continuous miners. Depillaring is carried out by longwall retreating method with caving, using powered supports on the face and shearer as the coal cutting machine. Although initially planned for a higher capacity, the present production has decreased to less than 1000 ton per day because of the inability of the operator to adopt modern underground mining technology. The mine is currently operating at a maximum depth of just over 600 m. The annual coal production is ~200,000 tons, which corresponds to an average daily production of ~700 tons. Recently, the mine has entered into technological collaboration with Zhengzhou Coal Mining Machinery Company Ltd (ZMJ) of China for mining coal at one of the seams. It is expected that, with technological assistance from ZMG, the production would increase to 700,000 ton per year, that is, >2000 tons per day, which would be a three-fold increase. The mine has two shafts, 7.5 m in diameter, one used as intake and the other as exhaust. The total quantity of airflow to ventilate all the working areas of the mine is ~12,000 m3/min. The mine is worked from three levels, known as horizons, 280 MH, 400 MH, and 500 MH. Although four seams are accessible from the mine, present operation is restricted to XV and XVI seams. The XVIII seam has already been extracted. The coal rank is bituminous, with estimated gas content of 6-15 m3/t of coal. One of the reasons for selecting Moonidih for this study was the CBM/CMM demonstration and recovery project in the vicinity. The pilot study, supported by Government of India, United Nations Development Project (UNDP) and Global Environmental Fund (GEF), has demonstrated the recovery of CBM from virgin seams of Moonidih using two vertical boreholes and feeding a generator to produce electricity. With success of this project, there is interest on the part of the mine operator to recover and utilize VAM. Moonidih, being a very old mine, has a large gob area containing large volume of mine gas with significant concentration of methane. Recovery of this CMM and mixing it with VAM may also enable maintain the methane concentration necessary for VAM utilization. Moreover the coal washing plant is located less than 250 m from the mine, providing a market for electricity produced by VAM. Finally, if hybrid combustion technology was to be found suitable, the washery can supply the coal middlings for combustion along with VAM.

4. VAM QUANTIFICATION STUDY To start with, mine plans were secured and studied to determine the methane monitoring locations. These locations included all exhaust routes, working faces/areas – main intakes and return – and development areas. The route for the mine-wide methane survey was decided on, and discussed with the mine personnel. This was followed by carrying out a mine-wide methane emission survey, as described in McPherson (1993). The survey included airflow measurements (Q-survey) throughout the mine, and measurement of methane concentration (c-survey) at every Q-station. Using the measurements, the amount of methane at each location was calculated. A thorough and rigorous technique was followed to assess the VAM emission from the mine. Samples were collected from the main return of the mine and analysed for concentration of VAM. For a six-month period, one measurement was taken every month, on a working day with full production. For one of the months, methane concentration was measured every week. For one of the weeks, the measurement was carried out every day, and for one of the days, the measurement was carried out every two hours. For a six-hour period, measurements were carried out every fifteen minutes. Hence, a complete array of methane concentrations data was obtained during the study. The measurements were taken in the mine exhaust system since this is the primary route for methane escape. The detailed measurements were used to calculate the quarterly/annual emission, as well as daily emission rate and thus, provided the overall

37

emission rate from the mine. Finally, The VAM emission results were correlated with the coal production data for the various periods in order to estimate the emission independent of production and that directly related to coal production. This was particularly critical since the mine production is expected to change significantly in the near future thus resulting in a change in the emission pattern.

5. RESULTS AND ANALYSIS

The study was conducted between December, 2007 and May, 2008. The hourly and daily samples were collected during December 11 to 18, 2008. The weekly samples, that is, hourly sampling on one day, every week of the month, were collected in the months of December, 2007 and January, 2008. The monthly samples, that is, hourly samples on one day of every month, were collected through May 2008. The coal production data was also collected for each sampling day. The exhaust samples were brought to the laboratory and analyzed within a few hours of collection. The analyzer used was capable of detecting methane accurately for concentration range of less than .054% to pure methane (100%). In order to estimate the dependence and correlation between the concentration of VAM and daily coal production, exhaust samples were also collected on an idle day, when there was no coal production. 5.1 VAM quantification Typical concentrations of VAM in the return air at different hours on two single days are shown in Figure 2. The upper plot shows the VAM concentration on a producing day,

0

0.04

0.08

0.12

0.16

0.2

10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00

Time (h:m)

VA

M C

on

cen

trat

ion

(%

)

Production

Base

Figure 2: Typical change in VAM concentration during a producing day

when 510 tons of coal was produced. The lower plot shows the variation of VAM concentration on an idle day. It is apparent that the methane concentration on the idle day was fairly constant and remained at 0.10% level. This is, therefore, also the minimum concentration on a producing day. During production day, the maximum concentration of VAM was measured to be ~0.20%. The range of variation in methane concentration with no coal production through ~500 tons production is, therefore, between 0.1-0.2 %. The total VAM emitted at the current rate of emission was calculated to be between 6.3-12.6 Mm3, as shown in Table 1. With coal production increasing to 2,100 tpd, the amount of methane emitted would vary in the range of 6.3-31.6 Mm3 (last column in Table 1), depending on idle time versus full-production time. There are two assumptions in these calculations. First, the increase in VAM concentration with production is linear at the rate of 0.1% per 500 ton of coal. This is a reasonable assumption since the amount of methane released from fresh coal mined is a function of production. Second, the future daily production of 2100 tons is actually achieved. Also, the airflow is not increased due to increased coal production. This is also a reasonable assumption since the overall airflow for the mine is adequate. It is the optimum distribution of

38

the airflow throughout the mine that is challenging. The VAM concentration for a 2100 ton daily production is thus estimated to be 0.5%, an encouraging finding at the mine. The minimum VAM concentration is also expected to go up from the present 0.1% level due to increase in working area as well as the amount of coal exposed. It is possible that the concentration level would increase to 0.2% or more, which is the lower cut-off required for application of any flow reversal technique. For the sake of completeness, the weekly and monthly variations are shown in Figures 3 and 4. it is apparent that the weekly variation is insignificant. However, the monthly variation is in the 0.14 and 0.18 range.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Week 1 Week 2 Week 3 Week 4

VA

M C

on

cen

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ion

(%

)

Figure 2. Weekly Variation of VAM concentration (December 2007)

0

0.04

0.08

0.12

0.16

0.2

January February March April May

VA

M C

on

cen

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ion

(%)

Figure 3: Monthly variation of VAM concentration (on producing days)

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Table 1. Current VAM Estimation

Details Production Current Production

Level Increased Production

(2100 tpd) Air Quantity 12,000 m3/min 12 000 m3/min Air discharged in one day 17.28 Mm3 17.28 Mm3 Air discharged in one year 6.3 Tm3 6.3 Tm3 VAM emitted @ 0.1% (V/V) 6.3 Mm3 6.3 Mm3 VAM emitted @0.2% (V/V) 12.6 Mm3 31.6 Mm3 Mean VAM estimate 9.4 Mm3 18.9 Mm3 Mean VAM estimate 6 342 t/yr 12683 t/yr CH4 destruction by TFRR 6 024 t/yr 12 049 t/yr CO2 equivalent emission reduction

10 9947 t/yr 219 893 t/yr

Carbon Credit earned @ $10/ton

1.10 M$/yr 2.20 M$/y

5.2 VAM utilization alternatives Any successful VAM utilization alternative would prevent the emission of 9.4 Mm3 of methane in one year at the current rate of coal production. However, the current emission rate of VAM is too low for application of the principal VAM utilization techniques, which require a minimum of 0.2% methane concentration at all times. Some of the ancillary use technologies may be used. Application of the Australian Hybrid coal/methane combustion technology appears to be promising because of the presence of the coal washing facility near the mine. The washery middlings may be burnt in a rotary kiln using the mine return air containing VAM as part of the combustion air. The economic feasibility of this alternative needs to be worked out. If, in fact, the target daily production of 2100 tons is achieved, the principal use technologies such as TFRR or the VAMOX can be applied. However, at many of the mines where TFRR system has been installed, energy has been recovered as heat and used for heating water and air. Neither of the two is currently available at the mine; nor is there a perceived need for hot air/water. Hence, recovering energy from VAM at the present time does not appear to be an attractive option. Installation of TFRR for destruction of VAM alone may be practiced to avail of the carbon credits. At >95% efficiency, the TFRR system would destroy 12,065 tons of methane per year. This is equivalent to reduction of 253,365 tons of CO2 equivalent emission and this would be eligible for carbon credit revenues. At $10/ton, this translates to a net revenue of ~$2.5 Million per year.

6. SUMMARY AND CONCLUSIONS

A systematic and detailed study was taken up at Moonidih mine to quantify the emission of VAM from the mine and assess the potential for use of VAM utilization technologies. The study demonstrated that a large quantity of VAM, an average 9.4 Mm3/year of methane is emitted from the mine at this time. However, the methane concentration varies between 0.1 and 0.2%. Since the minimum methane concentration is 0.1%, none of the principal use technology available to utilize VAM would be suitable. The application of ancillary use technology such as the Australian Hybrid technology can be studied further for its economic feasibility. The lower concentration of VAM is due to the low daily production of coal. This is expected to change drastically with the acquisition of technology from China in the near future with daily production of the mine expected to increase four-fold. If this were actually to happen, the principal use technology would become applicable. With installation of a TFRR system, the potential to earn carbon credits is significant.

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Based on the findings of the study, the authors believe that Moonidih mine has another potential source of methane. The mine is old with a large number of sealed off areas. The concentration of methane in these areas is fairly high. Furthermore, these areas “breathe”, suggesting that there is methane re-charge over time. A systematic study would, therefore, provide additional information for possible mixing with VAM as an enrichment technique for utilization.

7. ACKNOWLWDGEMENTS

This work was carried out as a result of funding from the US Environmental Protection Agency’s Climate Change Division. The authors wish to thank US EPA, in particular the Program Manager, Dr. Jayne Somers, for the support. The authors also wish to thank the management of Moonidih Mine for allowing this study at the mine and assistance provided during the study, particularly the Mine Manager, Mr. Supriyo Chkravarty.

8. REFERENCES CMRI, 2003, “Uncertainty in Reductions in Greenhouse Gas Inventories Associated to Coal Mining”.

Project report prepared as part of India’s Initial National Communication Project executed by Ministry of Environment and Forests, Government of India.

McPherson, M. J., 1993, Subsurface ventilation and environmental engineering, Chapman &Hall, London. Singh, A.K., Sahu, J.N. and Meikap, B. C., 2009 (in Press), Coal mine gas uses for hazardous waste

management in India, International Journal of Environment and Waste Management. Srivastava, M. and Harpalani, S., 2006, Systematic quantification of ventilation air methane and its

evaluation as an energy source, Mining Engineering, Vol. 58, No. 11, Nov., pp. 52-56 Su, S., Beath, A., Guo, H. and Mallett, C., 2005, An assessment of mine methane mitigation and utilisation

technologies, Progress in Energy and Combustion Science, Vol. 31, pp. S123–170. USEPA, 2003, “Assessment of the worldwide market potential for oxidizing coal mine ventilation air

methane”, EPA-430-R-03-002. USEPA, 2003, Coalbed Methane Extra, Fall 2003. USEPA, 2007, Coalbed Methane Extra, Spring 2007. USEPA, 2008, Coalbed Methane Extra, July 2008.

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Appendix II

Exhaust Methane Concentration Measurements

42

Measurements for Moonidih Mine

Date: Sample

No. Time CH4 % 11-Dec-07 1 10:30 0.054 2 11:30 0.108 3 12:30 0.135 4 13:30 0.135 5 14:30 0.162 6 15:30 0.162 7 16:30 0.162 8 17:30 0.135 9 18:30 0.135 Avg VAM= 0.13 Production, 11 Dec 2007 = 800 t

Date: Sample

No. Time CH4 % 18-Dec-07 1 10:30 0.081 2 11:30 0.108 3 12:30 0.108 4 13:30 0.151 5 14:30 0.162 6 15:30 0.162 7 16:30 0.135 Avg VAM= 0.13 Production on 18 Dec 07 = 720 t

Date: Sample

No. Time CH4 % 27-Dec-07 1 11:00 0.054 2 12:00 0.065 3 13:00 0.14 4 14:00 0.162 5 15:00 0.162 6 16:00 0.162 7 17:00 0.151 Avg VAM= 0.13 Production on 27 Dec 07 = 755 t

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Date: Sample

No. Time CH4 % 2-Jan-08 1 11:00 0.108 2 12:00 0.108 3 13:00 0.108 4 14:00 0.162 5 15:00 0.162 6 16:00 0.151 7 17:00 0.151 Avg VAM= 0.14 Production on 2 Jan 2008 = 735 t

Date: Sample

No. Time CH4 % 6-Jan-08 1 10:00 0.108 2 11:00 0.108 3 12:00 0.097 4 13:00 0.108 5 14:00 0.097 6 15:00 0.108 7 16:00 0.108 Avg VAM= 0.105 Production on 6 Jan 2008 = 0 (Idle Day)

Date: Sample

No. Time CH4 % 5-Feb-08 1 9:30 0.12 2 10:30 0.11 3 11:30 0.11 4 12:30 0.11 5 13:30 0.14 6 14:30 0.19 7 15:30 0.16 8 16:30 0.16 Avg VAM= 0.14 Production on 5 Feb 2008 = 735 t

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Date:

Sample No. Time CH4 %

5-Mar-08 1 9:30 0.12 2 10:30 0.11 3 11:30 0.14 4 12:30 0.14 5 13:30 0.14 6 14:30 0.16 7 15:30 0.19 8 16:30 0.19 Avg VAM= 0.15 Production on 5 March = 485 t

Date: Sample No. Time CH4 %

9-Apr-08 1 10:00 0.11 2 11:00 0.11 3 12:00 0.16 4 13:00 0.16 5 14:00 0.19 6 15:00 0.19 7 16:00 0.19 8 17:00 0.19 Avg VAM= 0.16 Production on 9 April 08 = 510 t

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Measurements for Sudamdih Mine

Return Air Sample from Sudamdih Mine Date of Sampling: 7 March 2008

Sample No. Time CH4 % 1 8:50 0.01 2 9:50 0.01 3 10:50 0.02 4 11:50 0.02 5 12:50 0.03 6 13:50 0.03 7 14:50 0.02 8 15:50 0.02 9 16:50 0.02 Average 0.02

Coal production = 120 t

Return Air Sample from Sudamdih Mine Date of Sampling: 27 March 2008

Sample No. Time CH4 %

1 8:45 0.02

2 9:45 0.02

3 10:45 0.02

4 11:45 0.02

5 12:45 0.04

6 13:45 0.04

7 15:40 0.04

8 16:40 0.02

9 17:40 0.02

Average 0.03

Coal production = 130 t

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Return Air Sample from Sudamdih Mine Date of Sampling: 3 April 2008

Sample No. Time CH4 %

1 10:00 0.02

2 11:00 0.02

3 12:00 0.03

4 13:00 0.03

5 14:00 0.03

6 15:00 0.02

7 16:00 0.02

8 17:00 0.02

Average 0.02

Coal production:100 t

Return Air Sample from Sudamdih Mine Date of Sampling: 2 May 2008

Sample No. Time CH4 %

1 7:50 0.02

2 8:50 0.02

3 9:50 0.02

4 10:50 0.02

5 11:50 0.02

6 12:50 0.02

7 13:50 0.02

8 14:50 0.02

9 15:50 0.02

Average 0.02

Coal production: Zero

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Return Air Sample from Sudamdih Mine Date of Sampling: 6 June 2008

Sample No. Time CH4 %

1 8:25 0.01

2 9:25 0.02

3 10:25 0.02

4 11:25 0.02

5 12:25 0.02

6 13:25 0.02

7 14:25 0.03

8 15:25 0.03

9 16:25 0.03

Average 0.02

Coal production:120 t

Return Air Sample from Sudamdih Mine Date of Sampling: 4 July 2008

Sample No. Time CH4 %

1 7:40 0.01

2 8:40 0.03

3 9:40 0.03

4 10:40 0.04

5 11:40 0.04

6 12:40 0.03

7 13:40 0.03

8 14:40 0.03

9 15:40 0.03

Average 0.03

Coal production:115 t

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49

Return Air Sample from Sudamdih Mine

Date of Sampling: 13 Aug 2008

Sample No. Time CH4 %

1 8:00 0.02

2 9:00 0.02

3 10:00 0.03

4 11:00 0.04

5 12:00 0.04

6 13:00 0.04

7 14:00 0.04

8 15:00 0.03

9 16:00 0.03

Average 0.03

Coal production:110 t

Date Avg. Conc. 7-Mar-08 0.02 3-Apr-08 0.02 2-May-08 0.02 6-Jun-08 0.02 4-Jul-08 0.03

13-Aug-08 0.03

Month Methane % Mar 0.02 Apr 0.03 May 0.02 Jun 0.02 Jul 0.03 Aug 0.03

Production Variation Month Production, t

Mar 120 Apr 130 May 100 Jun 120 Jul 115 Aug 110