The document summarizes a seminar presentation on fly ash utilization and disposal. Fly ash is a byproduct of coal combustion in power plants. It can be utilized in construction materials like concrete and bricks to replace resources like cement, clay, and sand. It can also be used to reclaim land or stabilize soil. However, much of the fly ash currently produced worldwide is disposed of in landfills or ash ponds, which can pollute air, water, and soil if not properly managed. The presentation discusses the composition, types, production, uses, disposal methods, and environmental impacts of fly ash.

1. SEMINAR PRESENTATION
FLY ASH : UTILIZATION AND DISPOSAL
Submitted by:
Jyoti kumari
Environmental Engineering
National Institute of Technology

2. Content:
 Introduction
 History
 Chemical composition
 Types of fly ash
 Ash generation and effects
 Production Process
 Utilisation
 Disposal
 Environmental consideration
 Advantages & disadvantages
 Conclusion
 References

3. Introduction
 Fly ash is one of the residues created during the
combustion of coal in coal-fired power plants.
 Fine particles rise with flue gasses and are collected
with filter bags or electrostatic precipitators
 Fly ash is a waste by-product material that must be
disposed of or recycled
 Fly Ash is considered as amorphous and mixture of
Ferro- alluminosilicate minerals.

4. History
The Roman Colosseum Ghatghar Dam

5. Chemical Composition
 Because fly ash is a by-product material chemical
constituents can vary considerably but all fly includes:
 Silicon Dioxide (SiO2)
 Calcium Oxide (CaO) also known as Lime
 Iron (III) Oxide (Fe2O3)
 Aluminum Oxide (Al2O3)
 Depending on source coal may include one or more toxic
chemicals in trace amounts:
 Arsenic, Beryllium, Boron, Cadmium, Chromium, Cobalt,
Lead, Manganese, Mercury, Molybdenum, Selenium,
Strontium, Thallium, and Vanadium

6. Types of Fly ash
 ASTM C618 Defines two classes of fly ash:
 Class C
 Class F
 ASTM C618 requirements:
 Loss of Ignition (LOI) < 4%
 75% of ash must have fineness of 45 µm or less
 Primary difference between Class C and Class F fly ash is the
amount of calcium, silica, alumina, and iron content in the ash

7. Class F
 Produced from burning harder, older anthracite and
bituminous coal.
 Contains less than 20% lime
 Requires cementing agent like PC, quick lime
, hydrated lime
 Used in high sulfate exposure conditions
 Used for structural concretes, HP concretes,
high sulfate exposure concretes
 Useful in high fly ash content concrete
mixes

8. Class C
 Produced from burning younger lignite and subbituminous
coal
 Higher concentration of alkali and sulfate
 Contains more than 20% lime
 Self-cementing properties
 Does not require activator
 Not for use in high sulfate conditions
 Primarily residential construction
 Limited to low fly ash content concrete
mixes

9. Ash Generation and Effects
 Ash is an inherited impurity of coal that will not burn. Typical
range is 5% to 40%
 Reduces handling and burning capacity.
 Increases handling costs.
 Affects combustion efficiency and boiler efficiency
 Causes clinkering and slagging.
 Ash is generated as the product of combustion of coal
 Comprises of 80% Fly Ash and 20% Bottom Ash
Parameter Indian Coal Indonesian
Coal
South African Coal
Ash content
(%)
38.63% 13.99% 17%

10. Scenario in India:

11. Production / Segregation process

12. Utilization
 In developed countries more than 80% Fly Ash is used for the
manufacturing following:-
 In agriculture
 Building material
 Bricks construction
 Mine fills
 Metallurgy
 Use of new material
 Environmental control
 Embankment

13. Details on Utilization
 Agriculture
 Indian Fly Ash is alkaline and as such improves soil quality. In a research
conducted by MSEB, it was found that with dose of 10MT per hectare and just
50% dose of chemical fertilizers there is increase of 20% yield in terms of grains
and fodder
 Mine Fills
 Utilization of Fly Ash in Mine fills has potential to consume large quantity of Fly
Ash. This single application of Fly Ash can utilise about 1/4th of total Fly Ash
generation
• Metallurgy
 The Fly Ash contains about 20%-25% alumina. CPRI Bengaluru has developed a
process to extract alumina from Fly Ash.
 About 1 tonne of Fly Ash with 400 kg of other additives like lime and gypsum can
produce 150 kg of alumina and 1250 kg of pozzolanic cement, which is a good raw
material for quality bricks

14.  Precast Fly Ash concrete units
 It can be used in production of various types of precast building units such as
solid and hollow core slabs, doors and window frames
 Clay Fly Ash Bricks
 About 0.25 – 0.80 times of calay can be replaced by fly ash.
 Further, the residual carbon content in Fly Ash brings about an economy in
fuel consumption during firing of bricks.
 Cement
 Fly Ash being an artificial pozzolanic material can be used for manufacturing
of Portland Pozzalona Cements (PPC), as partly replacement of cement in
mortar and concrete

15.  Building material
 Fly Ash is a Pozzolanic material containing silica in good proportion. It
has tremendous potential to be used as an alternative material for
building construction
 Road construction material
 Utilization of Fly Ash in bulk quantities for road works depending on the
intersection between Coal ash and sub-grade soil.
 Use of new material
 In order to maintain the present rate of technological development some
alternative materials viz., fly ash, fibre glass, reinforced plastics and glass,
reinforced gypsum are used as building materials.

16.  Embankment
 Lower unit weight reduces dead loads and induced settlement of sub-soil
 High shear strength compared with its low unit weight for good bearing
support
 Ease of placement and compaction can reduce construction time and cost
 Soil Stabilization
 A sheep’s foot roller is commonly used to add the fly ash to the soil.Also
specialized equipment can be utilized to pump fly ash or other stabilizers
into the soil.Class C fly ash is used in soil stabilization
 Flowable Fill
 Fly ash generally supplements the Portland cement in greater volume The
fine particulate of the fly ash acts as ball bearings allowing it to flow
freely. Generally Class C fly ash is used for flowable fill.

17. Fly ash use

18. Let us see what fly ash achieves in totality: -
 It delays the heat of hydration and hence reduces the thermal
cracks in concrete
 It improves the workability of concrete
 It makes the mix homogeneous and hence reduces segregation
and bleeding
 The concrete finish is improved due to perfectly spherical fly ash
particles
 The concrete permeability is substantially reduced which
enhances the life of the structure
 Fly ash contributes to the long term strength in concrete

19. Examples of fly ash utilization
Reclamation of saline soils using fly
ash (75% savings in Gypsum)
First fly ash embankment in the
country (Okhla fly over, New Delhi)

20. Examples of fly ash utilization
Upper dam of Ghatghar Pumped
Storage Scheme constructed with RCC
( 65% replacement of cement with fly
ash)
Use of Fly ash for Road Embankment

21. Disposal
 In the past fly ash produced from coal power plants was
simply entrained in flue gasses and released into the
environment. Now in the U.S., EPA regulations requires
greater than 99% of total fly ash produced in a plant to
be captured and either stored, recycled, or disposed.
 Worldwide, more than 65% of fly ash produced in the
world is disposed of in landfills or ash ponds.
 In India alone fly ash landfills comprise 65,000 acres of
land.

22. Modes of disposal
 Dry Fly Ash Disposal
Fly Ash once collected in Electrostatic Precipitator gets
transported to Fly Ash Bunkers using pressurized air and then
gets transported via truck or conveyers at the site and disposed
by constructing a dry embankment.
 Wet Fly Ash Disposal
Fly Ash once collected in ESP is mixed with water to form slurry
and then this slurry is transported through pipe to the ash ponds
or dumping areas near the plants.

23. Environmental Consideration of Disposal
 The environmental aspect of Fly Ash disposal aims at minimizing
air and water pollution.
 The Fly Ash produced by thermal power plants can cause all three
environmental risks-
Air : Air pollution is caused by direct emissions of toxic gases
from the power plants as well as wind-blown ash dust from ash
mound/pond.
surface water: The wet system of disposal in most power plants
causes discharge of particulate ash directly into the nearby
surface water system
ground water pollution. The long storage of ash in pond can
cause leaching of toxic metals from ash and contaminate the
underlying soil and ultimately the groundwater system

24. Schematically pathways of pollutant
movement around Fly Ash disposal.

25. Advantages of fly ash utilization
 Saving of space for disposal
 Saving of scare of natural resources
 Energy saving, firstly because the material is
automatically produced as a by-product and no
energy is consumed for its generation and secondly
because it can replace material which otherwise
would need to be produced by consuming energy.
 Protection of environment, as in construction it can
partly replace cement, production of which entails
energy consumption and CO2 emissions.

26. Disadvantages of fly ash utilization
 Groundwater contamination due to runoffs carrying ill-treated
fly ash.
 Cannot be used for structures requiring shorter setting time, a
demand which is expected by most of the engineers and
builders.
 It is very difficult to use in winter season due to further increase
in already longer setting time.
 Difficult to control colour of cement containing flyash. Hence,
a bit problematic to use where cosmetic quality plays a
significant role.

27. Conclusion
 Flyash can be proclaimed as one of the most advantageous
waste material.
 Using it as a construction material will not only help in its
disposal but will also add strength and durablity of
structures.
 Since, the current usage of flyash in India is still around
25% and below 45% even in the developed countries like
United States, there is a huge scope for flyash in upcoming
years.
 So let us harness a billion dollar resource that has been
wasted so far.

28. References
 http://www.flyash.com
 1st International Conference on Fly Ash Utilization, NDCC
Convention Centre, New Delhi held during November 24-25,
2011.
 Use of Fly Ash in Mine Filling- cbri
enviwww.cbrienvis.nic.in/mine_filling.htm
 Fly Ash Technologies- National Metallurgical Laboratory (A
constituent establishment of (CSIR)
 2nd Annual International Summit on Fly Ash Utilization, NDCC
Convention Centre, New Delhi held during January 17-18, 2013.