Reclamation of Coal Mines by Fly Ash –

An Experience in U.S.

“Optimum Utilization of Fly Ash by Power Plants”

“Fly Ash Utilization Conference & Expo Awards” March 15-16, 2018

Mission Energy Foundation Vivanta by Taj, Dwarka, New Delhi

Presenter Dr. Shiv Kumar Dube

Senior Fellow , TERI, New Delhi

Work and Contribution: Professor Barry E. Scheetz*

Materials Research Laboratory, Materials Research Institute,

The Pennsylvania State University,

University Park, Pennsylvania, USA

* With informal permission from

Conference Reference

About TERI

• TERI has a presence in different regions of

India with offices in Delhi, Mumbai,

Bangalore, Guwahati, Goa, Gurgaon, and

Mukteshwar. It is a highly regarded

research institution that has also

established a presence in North America,

Europe, Africa, Kuwait, and Japan.

• TERI has been at the forefront in providing

expertise and professional services to

national and international clients.

• Site: http://www.teriin.org/

About TERI’s-Mission

• Tackle issues of concernto Indian society, and the

world at large, and develop innovative and cost

effective solutions.

• Enhance networking for sustainable interventions.

• Realize potential for national and international

leadership as a knowledge based agent of change

in the fields of energy, environment, other natural

resources and sustainable development.

• Inspire and reach out to diverse stakeholders for

realizing a shared vision of global sustainable

development that could be translated into action.

About TERI

• TERI works closely with utilities, regulatory

commissions, government agencies, and

bilateral and multilateral organizations (e.g.,

The World Bank, Asian Development Bank,

Japan Bank for International Cooperation,

UK Department for International

Development, United Nations, and U.S.

Agency for International Development).

About TERI

• Dr. Ajay Mathur, TERI’s Director General was

previously the Director General of the Bureau

of Energy Efficiency in the Ministry of Power;

Senior Member and spokesperson for the

Indian negotiating team at COP-21 in Paris,

and Director of the Interim Secretariat of the

Green Climate Fund when it was initially

established. TERI has a strong reputation

with governments of foreign countries,

Central & State Government departments;

and National & International level

organizations and multilateral agencies.

India would continue to rely heavily on

coal based electricity generation

• Indian Power sector is dominated by coal

based thermal power plants, constituting

58.32% share ( ~1,92,972 MW) of total

installed capacity of ~3,30,861 Megawatt

(MW), as on December 31, 2017.

• In general, production of Indian coal

has increased by 7.5 times and

production of electricity has increased

by 13 times, since 1970-71

India would continue to rely heavily on

coal based electricity generation • Furthermore, Niti Aayog projects that the

total installed capacity for electricity generation in the country will range from 300-700 GW by 2047 under different policy initiative scenarios.

• Considering the practicality of implementation, even with best of efforts for flexibilation to diversify the fuel and technology mix in the power generation sector, India would continue to rely heavily on coal based electricity generation, accounting for at least 50-60% of the total capacity for many years.

Indian Coal Ash Scenario

• As per Ministry of Power, today, India’s Coal based thermal capacity is ~ 1,92,972 MW.

• And as per the data gathered by CEA for 155 coal/lignite based thermal power stations (installed capacity of 1,57,377 MW, the Ash generation for the year 2016-17 reported is 169.25 million tonne.

Indian Coal Ash Scenario

• As per CEA the utilization of fly ash has increased from 6.64 million tonne in 1996-97 to a level of 107.10 million-tonne by the year 2016-17 amounting to 63.28% which is behind the target set by MoEF&CC vide it’s notification dated 03.11.2009.

• The matching coal consumed was 509.46 million tonne indicating that the average ash content was 33.6% in the coal used by power stations.

Scope of Ash Utilization

• The avenues of fly ash utilization

such as in Building materials, Fly

ash bricks, Fly Ash Blocks, Panels,

Fly ash-concrete etc. provide limited

scope for Fly ash Utilization.

• The most reasonable solution for

maximum ash utilization seems to

be backfilling in mines.

Major Options for Ash filling

• Dry ash (moist) in Water pit of Mine

• Dry ash (moist) in Dry Pit of Mine

• Paste in Dry Pit of Mine

• Paste in Water Pit of Mine

• Slurry in Dry Pit of Mine

• Slurry in Water Pit of Mine

Reclamation of Coal Mines by Fly Ash –

An Experience in U.S.

• The Best Option for High Volume Fly Ash

Utilization is the Reclamation of Mine

through Coal Ash Backfilling.

• Here is a Case Study executed at Big

Gorilla Mine located in Pennsylvania, USA

Why Big Gorilla Mine?

• After careful evaluation the option No. 1 of Dry

ash (moist) in Water pit of Mine was chosen.

• This is a typical example of backfilling of coal

ash in mine filled with acidic water.

• It is pertinent to mention that there is a

legislation in West Virginia, USA that permit for

coal mining is granted only when the Coal

Mining Company agrees to take ash back in the

coal mine.

• Thus it is interesting to discuss the example of

Big Gorilla Mine.

Location of Big Gorilla Coal Mine in Pennsylvania, USA

Why Big Gorilla Mine?

• This mine was full of acidic water and had

witnessed the accident of children in the

mine.

• This backfilling has proved that mine filled

with acidic water is not the difficult case of

mine backfilling.

• The backfilling of this mine also proved that

the threat to the environment was

eliminated.

The Big Gorilla Mine pit • The Big Gorilla pit was an abandoned anthracite

surface mine located near Hazelton,

Pennsylvania in the Silverbrook Basin. It was

filled with about 427 m (1400 feet) long by 122 m

(400 feet) wide and 27.4 m (90 feet )deep.

• It was filled with about 4,23,966 m3 (120 million

gallon) of water that had been significantly

affected by AMD (Acid Mine Drainage). The

Silverbrook basin is approximately 8 km long and

1.6 km wide. It is drained by the Silverbrook

outfall which forms the headwaters of the Little

Schuykill River.

(Source Loop, Carline et al 2004)

The Big Gorilla Mine pit • This demonstration was dry to wet placement of

about 3 million tonne of Fluidized bed

combustion (FBC) ash into standing mine water.

Placement began in August 1997 and was

completed in 2004.

• The Ash was dumped into two working Platforms

by 45 tonne truck and then dozed into the pool.

As the mine pool was filled compaction was

accomplished. The ash came from Northern

eastern Power Company’s cogeneration facility in

McAdoo, Pennsylvania, which fires about 1700

tonne of coal refuse and 60 tonne of lime stone

per day. (Source Loop, Caroline et al 2004).

The Big Gorilla Mine pit • Five monitoring wells and three test boring

locations have been monitored continuously.

Numerous studies of mineralogy of the ash and

the evolution of the pit lake water chemistry have

been conducted the work used about 3 million

tonne of coal ash to eliminate the acid pool.

• The results included the possible reduction of the

acidity of the pool and decrease in some metal

concentration, a slight increase in some cations

and test of dry to wet placement.

• Some shots of Ash backfilling process could be

seen in next few slides.

(Source Loop, Carline et al 2004)

Spring 2001

Ash front

Boreholes

Closure status as of March 2002

Status of Closure as of February 2003

Ash input vs. pH in the Big Gorilla

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000Jul-97

Oct-

97

Jan-9

8

Apr-

98

Jul-98

Oct-

98

Jan-9

9

Apr-

99

Jul-99

Oct-

99

Jan-0

0

Apr-

00

Jul-00

Oct-

00

Jan-0

1

Apr-

01

Jul-01

Oct-

01

Jan-0

2

Apr-

02

Jul-02

Oct-

02

Jan-0

3

Date

Ash

in

pu

t (m

etr

ic t

on

s)

2

4

6

8

10

12

1497

97

98

98

98

98

99

99

99

99

00

00

00

00

01

01

01

01

02

02

02

02

03

pH

Ash Input

pH

Ash input vs. alkalinity in the Big Gorilla

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000Jul-97

Oct-

97

Jan-9

8

Apr-

98

Jul-98

Oct-

98

Jan-9

9

Apr-

99

Jul-99

Oct-

99

Jan-0

0

Apr-

00

Jul-00

Oct-

00

Jan-0

1

Apr-

01

Jul-01

Oct-

01

Jan-0

2

Apr-

02

Jul-02

Oct-

02

Jan-0

3

Date

Ash input

(metr

ic t

ons)

0

100

200

300

400

500

600

70097

97

98

98

98

98

99

99

99

99

00

00

00

00

01

01

01

01

02

02

02

02

03

Alk

alinity (

mg/L

CaC

O3)

Ash Input

alkalinity

Concentration

(mg/ L) 6/ 7/ 93 7/ 2/ 93 10/ 28/ 97 10/ 27/ 99 8/ 28/ 01

Al 3.5 4.2 0.57 0.38 0.41

Fe 0.52 0.40 0.11 < 0.020 0.15

Mn 0.71 0.72 0.011 0.010 0.014

Zn 0.22 0.20 0.008 0.052 < 0.010

* pH of water with ash -- 12.0

* pH of water in Gorilla Mine -- 12.1

Results from borehole testing of placed ash:

* The ash has a water table at the level of the Gorilla

* Capillary draw wets the ash above the water table

* The top 2 feet are hardened

X

X

X

X X

X

X X

X X

Field Bearing Capacity Testing

[average >10,000 psf]

Silverbrook Outfall

Ref: Coal ash beneficial use at mine sites in Pennsylvania, Roger J. Hornberger et al.; 2005 World of Coal Ash April 11-15, 2005

Ref: Coal ash beneficial use at mine sites in Pennsylvania, Roger J. Hornberger et al.; 2005 World of Coal Ash April 11-15, 2005

An important agency to support such work • Mine Land Reclamation Center (NMRC) founded

by U.S. Congress in 1988 to deal with water

quality issues associated with coal mining.

• Headquartered at West Virginia University,

Morgantown, West Virginia.

• Director, Dr. Paul F. Ziemkiewicz

• NMLRC as a “Team Leader” of the US

Consortium formed by the USDOE/ US AID had

earlier conducted a feasibility study for filling

ash of NTPC Singrauli into Gorbi Mines of

Northern Coalfields Limited (NCL). The other

members of the consortium were Pennsylvania

State University, USA and HMI - A Hydrogeology

Expert.

An important agency to support such work

• National Mine Land Reclamation Center

(NMLRC)

• US DOE/ US AID provided technical and

financial support to do the project.

• The report was submitted to the

concerned authorities

• It recommend that Gorbi mine project is

a doable project and need to be taken up

as early as possible to avoid the damage

to the environment, specially the

prevailing underground water system.

Conclusions:

• Ash was structurally stable.

• High pH and alkalinity in Big Gorilla water

due to Ca(OH)2.

• Fe, Al, Mn, and Zn are decreased.

• No evidence of chemical change in the

Silverbrook outfall directly related to ash

placement in the Big Gorilla.

• The ash placement would decrease the

production of AMD and remove a surface

hazard.

Acknowledgement:

Profuse thanks are due to Prof. Barry E.

Scheetz of Pennsylvania State

University, USA for his candid Support.

Shivkumar.dube@teri.res.in March 15, 2018