January 2007
State Environment Related Issues
Vol.2 No. 6
DEPARTMENT OF FORESTS, ECOLOGY & ENVIRONMENT, GOVERNMENT OF KARNATAKA ENVIS Newsletter
ly ash is one of the numerous
substances that cause air, water and
soil pollution, disrupt Fecological cycles and set off
environmental hazards.
The combustion of powdered coal
in thermal power plants produces fly ash.
The high temperature of burning coal turns
the clay minerals present in the coal powder
into fused fine particles
mainly comprising
aluminium silicate. Fly
ash produced thus
possesses both ceramic
a n d p o z z o l a n i c
properties.
When pulverised coal is
burnt to generate heat, the
residue contains 80 per
cent fly ash and 20 per
cent bottom ash. The ash
is carried away by flue gas collected at economiser, air
pre-heater and ESP hoppers. Clinker type ash collected in
the water-impounded hopper below the boilers is called
bottom ash.
The World Bank has cautioned India that by 2015,
disposal of coal ash would require 1000 square
kilometres or one square metre of land per person. Since
coal currently accounts for 70 per cent of power
production in the country, the Bank has highlighted the
need for new and innovative methods for reducing
impacts on the environment.
The process of coal combustion results in fly ash. The
problem with fly ash lies in the fact that not only does its
disposal require large quantities of land, water, and
energy, its fine particles, if not managed well, by virtue of
their weightlessness, can become airborne. Currently, 90
million tonnes of fly ash is being generated annually in
India, with 65 000 acres of land being occupied by ash
ponds. Such a huge quantity does pose challenging
problems, in the form of land usage, health hazards, and
environmental dangers. Both in disposal, as
well as in utilization, utmost care has to be
taken, to safeguard the interest of
human life, wild life, and
environment.
Is fly ash hazardous?
The physical, geotechnical and chemical
parameters to characterize fly ash are the same as those
for natural soils, e.g., specific gravity, grain size,
Atterberg limits, compaction characteristics,
permeability coefficient, shear strength parameters and
consolidation parameters. The properties of ash are a
function of several variables such as coal source, degree
of pulverization, design of boiler unit, loading and firing
conditions, handling and storage methods. A change in
any of the above factors can result in detectable changes
in the properties of the ash produced. The procedures for
determination of these parameters are also similar to
those for soils.
FLY ASH
Specific gravity 1.90-2.55
Plasticity Non Plastic
Proctor compaction - Maximum
dry density (gm/cc) 0.90-1.60
Optimum moisture content (%) 38.0-18.0
Angle of internal friction ( O) 300-400
Cohesion (kg/cm 2 ) Negligible
Compression index 0.05-0.4
Permeability (CM/SEC) 105-103
Particle size distribution
Clay size fraction (%)
Silt size fraction (%)
Sand size fraction (%)
Gravel size fraction (%)
1-10
8-85
7-90
0-10
Coefficient of uniformity 3.1-10.7
Engineering properties of Fly Ash
Parameter
Nearly 73% of India's total installed power generation capacity is thermal, 90% of it coal-based
Utility bonanza from dust
2
How fly ash is hazardous
Fly ash is a very fine powder and tends to travel far in the
air. When not properly disposed, it is known to pollute air
and water, and causes respiratory problems when inhaled.
When it settles on leaves and crops in fields around the
power plant, it lowers the yield.
The conventional method used to dispose of both fly ash
and bottom ash is to convert them into slurry for
impounding in ash ponds around the thermal plants. This
method entails long-term problems.
The severe problems that arise from such dumping are:
Ground water aquifer
Surface water
Ash mound/
pond
Deep soil
Surface soil
Air
Wind
transport
Atmospheric
fall-out
Atmospheric
fall-out
Wind
transport
Surface run-off
Surface run-off
Infiltration Leaching
Dispersion and Diffusion
How dumping of fly ash leads to pollution of air, land and water
India would require 1000 sq Km / 1 Sq m per person for disposal of coal ash by 2015.
Fly ash produced during the burning of powdered coal in thermal power plants is a hazardous waste.
However, its physical and chemical properties make it an ideal raw material for producing high quality and
cost-effective bricks, interlocking pavers, kerbstones and mosaic tiles.
Rajiv Gandhi Rural Housing Corporation Ltd. has done pioneering work in using fly ash products in
the projects implemented by it. Fly ash-based building components like blocks, bricks, door and window
frames are extensively used in the construction of houses in Raichur, Bellary, Uttara Kannada and Shimoga
Districts. Raichur Nirmiti Kendra received an award from HUDCO for use of industrial waste as building
material.
The effort of ENVIS Centre, Karnataka, to popularize the use of fly ash products is laudable.
Shri Nilaya Mitash, I.A.S.,
Managing Director
Rajiv Gandhi Rural Housing
Corporation Ltd.,
Cauvery Bhavan
Bangalore.
15 March 2007
(Nilaya Mitash)
3
® The construction of ash ponds requires vast tracts of
land. This depletes land available for agriculture
over a period of time.
® When one ash pond fills up, another has to be built,
at great cost and further loss of agricultural land
® Huge quantities of water are required to convert ash
into slurry.
During rains, numerous salts and metallic content in the
slurry can leach down to the groundwater and
contaminate it.
Disposal problem
The Raichur Thermal Power Station (RTPS), one of
Karnataka's major power plants, is situated at
Shakthinagar near Devasugur village in Raichur District.
Owned by Karnataka Power Corporation Limited
(KPCL), RTPS consists of seven units, each capable of
generating 210 MW of power. Its total power generation
at optimum capacity is 1470 MW per day. RTPS is the
power-generating hub of Karnataka and meets 75 per cent
of the state's power demand.
India has about 70 thermal power plants and 70 per cent of
them burn coal to generate power. Various Indian
collieries supply the coal, which is known to have a very
high ash content of almost 40 to 45 per cent.
India's thermal power plants produce an estimated 100
million tonnes of fly ash per annum. Of this, RTPS alone
generates about 1.5 million tonnes at 4,000 tonnes daily.
Out of this, 80 per cent is fly ash and 20 per cent bottom
ash. This ash needs to be disposed of every day.
Primarily, the fly ash is disposed of using either dry or wet
disposal scheme. In dry disposal, the fly ash is transported
by truck, chute or conveyor at the site and disposed of by
constructing a dry embankment (dyke). In wet disposal,
the fly ash is transported as slurry through pipe and
disposed of in impoundment called "ash pond". Most of
the power plants in India use wet disposal system, and
when the lagoons are full, four
basic options are available:
† constructing new lagoons
u s i n g c o n v e n t i o n a l
construction material,
† hauling of fly ash from the
existing lagoons to another
disposal site,
† raising the existing dyke using
conventional constructional
material, and
† raising the dyke using fly ash
excavated from the lagoon
(’ash dyke’).
The option of raising the existing dyke is very cost
effective because any fly ash used for constructing dyke
would, in addition to saving the earth filling cost, enhance
disposal capacity of the lagoon.
An important aspect of design of ash dykes is the internal
drainage system. The seepage discharge from internal
surfaces must be controlled with filters that permit water
to escape freely and also to hold particles in place and the
piezometric surface on the downstream of the dyke. The
internal drainage system consists of construction of rock
toe, 0.5m thick sand blanket and sand chimney. After
completion of the final section including earth cover the
turfing is developed from sod on the downstream slope.
Fly Ash Mission:
The Government of India, through the Department of
Science and Technology, has initiated the Fly Ash
Mission, under TIFAC. The mission propagates various
developments in the area of fly ash utilization carried out
by the R & D institutes in India. Besides, the political will
to encourage the use of fly ash has risen perceptibly.
The Fly Ash Mission was commissioned in 1994 with the
Department of Science & Technology (DST) as the nodal
agency and Technology Information and Assessment
Council (TIFAC) as the implementing agency, in view of
the overall concern for the environment and the need for
the safe disposal and effective utilization of fly ash.
Technology Project in Mission Mode (TPMM)
The Ministry of Environment & Forest (MoEF), Ministry
of Power, thermal power stations, R&D institutions and
industry together have launched a Technology Project in
Mission Mode (TPMM). Their focus is on the
demonstration of coal ash related technologies for
infusing confidence and thus ensuring large-scale
adoption. The industry, R&D institutions and academia
have obtained encouraging results from several projects
they have taken up. Some of these projects have been
completed, multiplier effects have started and other
projects are heading towards meaningful completion. A
Approximate 100 million tonnes of fly ash is generated in India’s thermal power plant per annum
Raichur Thermal Power Station, Raichur
judicious mix of thrust areas has been taken up for
concerted efforts. These include fly ash characterization;
hydraulic structures; handling and transportation;
agriculture related studies and application; ash ponds and
dams, reclamation of ash ponds for human settlement,
roads and embankments, underground mine fills and
related research projects.
Utilization is a viable alternative to dumping
Several factors have impeded fly ash utilization in India,
while it is being extensively used globally. Coal-based
thermal power stations have been operational for more
than 50 years but the concept of developing environmentfriendly
solutions for fly ash utilization is only about 15
years old. Overall fly ash utilization in India stands at a
fairly low level of about 15 per cent of the quantity
generated. Various possibilities for its use are under
research. Among numerous factors that account for the
low level of utilization, the chief factors are:
E Poor understanding of the chemistry of fly ash and its
derivatives for proper end applications
E Absence of standards and specifications for fly ash
products
E Lack of reliable quality assurance for fly ash products
E Poor public awareness about the products and their
performance
E Non-availability of dry fly ash collection facilities
E Easy availability of land with top soil at cheap rates
for manufacturing conventional bricks
E Lack of proper coordination between thermal plants
and ash users.
Fly ash utilization in the country is gaining momentum
owing to the stringent regulations that the MoEF has
stipulated, as also to increased awareness about the
benefits of using fly ash for various products.
Fly ash from coal-fired thermal power stations is an
excellent potential raw material for the manufacture of
construction material like blended cement, fly ash
bricks, mosaic tiles and hollow blocks. It also has
other, high volume applications and can be used for
paving roads, building embankments, and mine fills.
Fly ash products have several advantages over
conventional products. The use of cement in the
manufacture of construction products can be reduced
by substitution with fly ash. While the use of cement
cannot be completely avoided, for certain products
like tiles, the substitution can go up to 50 per cent.
These products are known to be stronger and more
cost-effective because of substantial savings on raw
material.
Fly ash products are also environment-friendly. A case
in point is fly ash bricks. The manufacture of
conventional clay bricks involves the consumption of
large amounts of clay. This depletes topsoil and
degradation of agricultural land. Fly ash bricks do not
require clay and serve two purposes; preservation of
topsoil and constructive utilization of fly ash.
Agricultural uses of fly ash
Research on agricultural uses of fly ash has been going on
in universities and research institutes (see box) across the
country for several years.
The same fly ash that causes harm when it settles on
leaves, can prove beneficial when applied scientifically
to agricultural fields. It can be a soil modifier and enhance
its moisture retaining capacity and fertility. It improves
the plant's water and nutrient uptake, helps in the
development of
roots and soilbinding,
stores
carbohydrates
and oils for use
when needed,
p r o t e c t s t h e
plants from soilborne
diseases,
and detoxifies
contaminated
soils.
Yields are also
known to increase, as experiments on groundnut,
sunflower, linseed and other oilseeds have shown.
Fly ash as fill material
Large scale use of ash as a fill material can be applied
where
ö Fly ash replaces another material and is therefore in
direct competition with that material.
ö Fly ash itself is used by the power generating
company producing the fly ash to improve the
economics of the overall disposal of surplus fly ash.
4 Full utilisation of generated fly ash in India, will provide employment potential for 3000 people.
Filling fly ash into trucks
5
ö Fly ash disposal is combined with the rehabilitation
and reclamation of land areas desecrated by other
operations.
Fills can be constructed as structural fills where the fly
ash is placed in thin lifts and compacted. Structural fly ash
fills are relatively incompressible and are suitable for the
support of buildings and other structures. Non-structural
fly ash fill can be used for the development of parks,
parking lots, playgrounds and other similar lightly loaded
facilities. One of the most significant characteristics of
fly ash in its use as a fill material is its strength. Wellcompacted
fly ash has strength comparable to or greater
than soils normally used in earth fill operations. In
addition, fly ash possesses self-hardening properties
which can result in the development of shear strengths.
The addition of illite or cement can induce hardening in
bituminous fly ash which may not self-harden alone.
Significant increases in shear strength can be realized in
relatively short periods of time and it can be very useful in
the design of embankments.
Fly ash in portland cement concrete
Fly ash can be used in portland cement concrete to
enhance the performance of the concrete. Portland
cement is manufactured with calcium oxide (CaO), some
of which is released in a free state during hydration. As
much as 20 pounds of free lime is released during
hydration of 100 pounds of cement. This liberated lime
forms the necessary ingredient for reaction with fly ash
silicates to form strong and durable cementing
compounds, thus improves many of the properties of the
concrete. Some of the resulting benefits are:
Ä Higher ultimate strength
Ä Increased durability
Ä Improved workability
Ä Reduced bleeding
Ä Increased resistance to
sulfate attack
Ä Increased resistance to
alkali-silica reactivity
Ä Reduced shrinkage.
Fly ash utilization, especially in
concrete, has significant
benefits including: (1)
increasing the life of concrete
roads and structures by
improving concrete durability,
(2) net reduction in energy use
and greenhouse gas and other
adverse air emissions when fly
ash is used to replace or
displace manufactured cement,
(3) reduction in amount of coal
combustion products that must
Conversion of fly ash into wealth generator
(Excerpt from President A P J Abdul Kalam's
address to the nation on the eve of the country's
56th Republic Day):
“As you are aware, the use of coal for power
generation results in an increased quantum of fly
ash production, which has reached about 100
million tonnes per year. All out efforts are needed
to utilize this fly ash not only from environmental
considerations, but also to avoid land usage for fly ash dumping. Though there
has been a steady progress in fly ash utilization from 1990, we have a long way
to go to reach the target of 100 per cent fly ash utilization. It is reported that the
agricultural increase of grains is around 15 per cent, green vegetables 35 per
cent and root vegetables 50 per cent, when fly ash is mixed with soil. Toxicity
tests have proved that there is no toxic element due to fly ash. But it has higher
nutrients due to increased availability of iron and calcium. Fly ash can become a
wealth generator by making use of it for producing ‘green building’ materials,
roads, agriculture etc. Full utilization of the generating stock will provide
employment potential for three hundred thousand people and result in a
business volume of over Rs.4,000 crore.”
Full utilisation of fly ash in India, will result in a business volume of over Rs. 4,000 crore.
Typical cross section of fly ash road
embarkment
Typical cross section of flexible pavement
- using fly ash
Typical cross section of regid pavement
- using fly ash
Fly ash road embarkment
be disposed in landfills, and (4) conservation of other
natural resources and materials. Typically, 15 to 30 per
cent of the portland cement is replaced with fly ash.
Fly ash for roads
Fly ash can be used for construction of road and
embankment. This utilization has many advantages over
conventional methods.
² Saves top soil which otherwise is conventionally
used
² Avoids creation of low lying areas (by excavation of
soil to be used for construction of embankments)
² Avoids recurring expenditure on excavation of soil
from one place for construction and filling up of low
lying areas thus created.
² Does not deprive the nation of the agricultural
produce that would be grown on the top soil which
otherwise would have been used for embankment
construction.
² Reduces the demand of land for disposal/deposition
of fly ash that otherwise would not have been used
for construction of embankment.
² Controls the source of pollution.
Manufacturing process of a typical fly ash product
Mosaic tile manufacture involves preparing the mix for
two layers: the wearing layer and the base layer. The
wearing layer consists of a plastic mix of mosaic chips,
cement, and fly ash and dolomite powder. The base layer
consists of a semi-dry mix of fly ash, cement and quarry
dust. The tiles are pressed in the tile-making machine and
air-dried for 12 hours or more. They then undergo curing
CASHUTEC and INEP
ne small step in addressing this issue. Special thanks to the Indo-Norwegian Environment Programme
(INEP) for setting up the Centre for Ash Utilization Technologies and Environment Conservation o(CASHUTEC) at the Raichur Thermal Power Station and thereby combating the fly ash hazard.
The establishment of CASHUTEC at the Raichur power station is one of the several projects that INEP has
initiated in Karnataka. Through its projects, it aims to address air, water and soil pollution and promote
sustainable solutions. All INEP projects are pilot in nature and contribute to sustainable management of natural
resources.
.
The project at RTPS had the following objectives :
† Establishing a self-sustaining fly ash utilization demonstration centre
† Functioning as a nodal centre for development, demonstration, training and transfer of technologies for fly
ash utilization in India
† Bringing increased awareness among entrepreneurs and various end users about the benefits of using fly
ash products
† Reducing potential threats of air and water pollution
† Ensuring the ecological and environmental stability of areas surrounding RTPS
† Reducing pressure on land requirements for fly ash dumping.
Objectives of CASHUTEC
CASHUTEC itself was established with the broad objectives of:
† Conducting R & D programmes on uses of fly ash
† Demonstrating manufacture of fly ash building products
† Demonstrating high volume uses of fly ash in cement, concrete,
agriculture and building of roads
† Generating increased awareness on the benefits of using coal ash
products among entrepreneurs and various end-users from four
of Karnataka's northern districts, Raichur, Bellary, Gulbarga
and Dharwad
† Enabling semi-commercial production of bricks, blocks, pavers
and mosaic tiles for self-sustenance of the centre
† Developing a strong brand for products manufactured at the
centre.
Total cost Rs.580.00 lakhs
INEP assistance Rs.225.00 lakhs
KPCL
contribution
Rs.355.00 lakhs
Duration Two years
Total cost Rs.26.00 lakhs
INEP assistance Rs.19.00 lakhs
CASHUTEC
contribution
Rs.7.00 lakhs
Duration 18 months
Financial Outlay of the Project
Phase one
Phase two
6 Orissa Government has banned the use of soil for brick manufacturing upto 70 km of a thermal power station
7
in water tanks for 15 days. The tiles are then
polished and stacked for supply.
While the procedure may be similar to the
conventional method, the substitution of cement
with fly ash by up to 30 per cent serves as value
addition. Fly ash is used in both layers of a mosaic
tile. Several benefits accrue from this. Fly ash turns
from a problem ridden byproduct into a component
of a utility product comparable to conventional
products in strength and aesthetics. Fly ash tiles,
for example, can be used for heavy-duty floors too.
The table below suggests that the properties of fly
ash mosaic tiles are far superior to those of
conventional tiles.
FAL-G (fly ash-lime-gypsum)
Fal-G bricks and blocks are manufactured without
using thermal energy, in contrast to the sintering
involved in the production of clay bricks.
How do these bricks get strength, if they are not
baked?
Fal-G bricks are made of a mixture of fly ash-limegypsum
or fly ash-cement-gypsum. In either
combination, Fal-G is a hydraulic cement, which
means it sets and hardens in the presence of
moisture, on the lines of ordinary portland cement,
gaining strength progressively over ageing. Nearly
200 tonnes of coal is used to sinter one million clay
bricks, a process that generates over 350 tonnes of
carbon dioxide (CO2). The production process of
Properties
Fly ash
mosaic
tiles
IS 1237/CPWD specs
Wet transverse
strength (N/sq. mm)
4.5 Not less than 3.0 N/sq. mm
when full size tiles are tested
Water obsorption(%) 3.3 Not to exceed 10% when full
size tiles are tested
Abrasion resistance
(mm)
1.75 Not to exceed 3.5 mm for
general purpose. Not to exceed
2.0 mm for heavy duty tiles.
Evaluation results of fly ash mosaic tiles
Fly ash Product Characte ris tics CASHUTEC Convential
Finish Excellent Satisfactory
Compressive strength 65 - 100 kg/cm2 50 kg/cm2
Water absorption 10 - 12% 15 - 20%
Finish Excellent Satisfactory
Compressive strength 50 kg/cm2 35 kg/cm2
Water absorption 10 - 12% 13 - 15%
Finish Excellent Good
Compressive strength 170 - 280 kg/cm2 150 - 200 kg/cm2
Water absorption 10 - 12% 0.15
Finish Excellent Good
Compressive strength 215 kg/cm2 150 kg/cm2
Water absorption 8 - 10%
Finish Excellent Good
Transverse Strength 15 kg/cm2 30 kg/cm2
Water absorption 3 - 4% 0.1
Abrasion resistance 1.75 mm 3.5 mm
Mosaic tile
Te chno e conomic analys is and comparative study of
fly ash products manufacture d at CASHUTEC
Brick (9 x 4.25 x 3) inches
Block (16 x 8 x 8) inches
Interlocking paver
Kerbstone
Mosaic tiles Interlocking pavers
Fly ash blocks Fal-G blocks
Fly ash products manufactured at CASHUTEC, Raichur
World Bank has offered to buy 800,000 tonnes of CO reductions from utilisation of Fly ash. 2
ENVIS Centre - Karnataka
Department of Forests, Ecology & Environment, Government of Karnataka
O/o Indo Norwegian Environment Programme, 2nd floor, Parisara Bhavan ,
No 49, Church Street, Bangalore - 560 001. Karnataka
Ph: 080-2559 1515 email: enviskar@dataone.in URL: http://www.parisaramahiti.kar.nic.in
Fal-G bricks eliminates harmful emissions of this
scale. This would also be the amount of carbon
credit earned
Frequently Asked Questions
What is fly ash?
Fly ash is a fused residue of clay minerals present
in coal. The high temperature generated when
coal burns in thermal power plants, transforms the
clay minerals in coal powder into a variety of
fused fine particles of mainly aluminium silicate
composition.
Is fly ash harmful?
Fly ash is a very fine powder and tends to travel in
the air. When not properly disposed of, it pollutes
air and water, and causes respiratory problems
when inhaled. When it settles on leaves and crops in
agriculture fields around the power plant, it lowers the
yield.
Where and how can fly ash be sourced?
Fly ash can be sourced free of cost from RTPS, Raichur
in Karnataka .
Which is the nodal agency for all fly ash related
queries?
CASHUTEC at Shaktinagar, Raichur is the nodal
agency for all queries related to fly ash utilization. This
includes technical know-how, queries about
technology, machinery, manufacture and usage.
What makes fly ash useful?
Fly ash is most commonly used as a pozzolan in PCC
applications. Pozzolans are siliceous or siliceous and
aluminous material, which in a finely divided form and
in the presence of water, react with calcium hydroxide at
ordinary temperatures to produce cementitious
compounds.
What are Carbon credits?
Carbon credits are certificates awarded to countries that
are successful in reducing the emissions that cause
global warming. For trading purposes, one credit is
considered equivalent to one tonne of carbon dioxide
emission reduced. Such a credit can be sold in the
international market at a prevailing market rate. The
trading can take place in open market. Developed
countries that have exceeded the levels can either cut
down emissions, or borrow or buy carbon credits from
developing countries. However there are two exchanges
for Carbon credit viz Chicago Climate Exchange and
the European Climate Exchange.
Is it possible to set up industries to manufacture
products similar to those produced by
CASHUTEC?
Yes, CASHUTEC provides complete technical and
commercial consultancy for prospective entrepreneurs
who wish to set up industries for the manufacture of fly
ash products.
Is it possible to procure products manufactured at
CASHUTEC?
Yes, it is possible to order and procure products from
CASHUTEC, or through the GRASIM Industries
dealer network.
Source:
[1]Using fly ash Extracting value from waste
Published by INEP.
[2] Extract from paper 'Technology: Fly ash Disposal
and Utilization: The Indian Scenario' by Rajiv
Sinha, Department of Civil Engineering, IIT
Kanpur
[3] Excerpt from Kiln Economics, Down to Earth July
15, 2005
[4] Wikipedia.org
[5] www.tifac.org.in
ENVIS Team:
Chakravarthi Mohan K.A.S., Co-ordinator, ENVIS
Centre,
Vijay Bhat, Programme Manager, Indo Norwegian
Environment Programme,
K.N. Koushik, IT Assistant.
Seetha Subbaraju memorial hall in Raichur
constructed using fly ash products
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