ENERGY TECHNOLOGY

S.JITENDRA PAL
Assistant Professor

Department of Chemical Engineering

National Institute of Technology Karnataka
Surathkal-Karnataka.

Fundamentals of energy and its impact

on society and the environment.

What is energy?
Energy :defined as the ability or capacity to do work.
Energy is measured in BTU (British Thermal Unit) or Joule
According to Max Planck, energy is defined as the ability
of a system to cause external action.
The term energy carrier thus a carrier of the above
defined energy is a substance that could be used to
produce useful energy, either directly or by one or
several conversion processes
In this respect the following forms of energy are
distinguished: mechanical energy (i.e. potential or
kinetic energy), thermal, electric and chemical energy,
nuclear energy and solar energy etc.

Why Energy is needed ?

Think about how you use energy every day. You
wake up to an alarm clock. You take a shower
with water warmed by a hot water heater. You
listen to music on the radio as you dress , u eat
breakfast.. And so on.
Food items, medicines, groceries, the accessories
which we use, Cosmetics, electronic appliances,
lighting, heating cooling,
Everything needs energy in direct or indirect way

Why Energy is needed ?

Various sectors of economy- Industry, residential,
commercial, transport
Industry- Petroleum Refining , steel, cement,
chemical, metal, paper, pharmaceuticals, mining
etc
Transportation,-automobile,
commercial
transport,-bus , truck, train, airplane , mass
transits
Residential and commercial buildings use energy
in for heating and cooling, lighting, heating water,
and operating appliances.

Non-Renewable Energy Sources

Conventional
Petroleum
Natural Gas
Coal
Nuclear

Unconventional (examples)
Oil Shale
Natural gas hydrates in marine sediment
6

Renewable Energy Sources

Solar photovoltaics
Solar thermal power
Passive solar air and water heating
Wind
Hydropower
Biomass
Ocean energy
Geothermal
Waste to Energy

World Energy Scenario

World primary energy demand grows by 1.6%
per year on average between 2006 and 2030
an increase of 45%

The worlds energy needs would be well over

50% higher in 2030 than today. China and India
together account for 45% of the increase in
global primary energy demand in this scenario.
- World Energy Outlook ( www.iea.org )

Indian Energy Sector

Some facts

India - one of the fastest growing economies in the

world. It is poised to grow at around 7 percent on
moderate term.
Indias Energy Consumption is 12.6 million btu.
India energy intensity is higher compared to Japan, USA
and Asia as a whole by 3.7, 1.55 and 1.47 times
respectively (energy consumption compared to GDP).
This indicates inefficient use of energy but also
substantial scope of energy savings.
Long term energy plan for India therefore should aim at
a) Projecting the energy demand
b) Projecting the energy mix
c) Exploring the possibilities for alternative sources and
d) Suggesting measures for energy efficient uses

Peak Production of Petroleum in US

10

Projected World Peak Production of

Petroleum

11

12

1999 Regional Shares of Crude Oil Production

(3445 Mt)

13

14

World Total Primary Energy Supply in 1998

(9491 Mtoe)

**Other includes geothermal, solar, wind, heat, etc.

15

World Energy Consumption

16

World Energy Consumption

17

World Total Energy Consumption 1990 2020 (Quadrillion Btu)

Region/Country
United States
Western Europe
Japan
China
Former Soviet Union
Total World
18

1990
84.0
59.9
18.1
27.0
61.0
346.7

1997
94.2
64.0
21.3
36.7
40.8
379.9

2020
120.9
78.4
25.4
97.3
57.3
607.7

U.S. Energy Flow, 1999

19

U.S. Energy Consumption by Source, 1998

20

Primary Commercial Energy Mix (%)

Resources

Oil
Natural Gas
Coal
Nuclear
Hydel

World V/S India

World

India

37.4
24.3
25.5
6.5
6.3

33.22
9.34
53.54
1.04
2.63
Source : www. planningcommission.gov.in

Indian Energy Sector

Vision of Some Eminent Experts..

The energy scene in the 21st century is going to see a

major shift. Very soon, oil and gas will see its finiteness. It is
high time that we realize this factor and work towards the
fuel of the future.
- Dr. A P J Abdul Kalam, Former President of India, Address
at Energy Technology Conclave Technology for Sustainability

If we expect our economy to keep growing at 9-10% p.a.,

we need a commensurate growth in power supply. The
power sector has made good progress over the past few
years. It has also seen very significant changes. However we
have not been able to make a decisive breakthrough in
ensuring high and sustainable rates of growth of this sector
and improving its financial health.
- Honble Prime Minister Dr. Manmohan Singh

Energy Potential Shape of Things to Come

India's energy potential is rated the third largest in
the world, with annual installations of 875 mega
watts (MW), only after Europe and the United
States, exceeding forecasts of 500 MW - BTM
Consult.
A recent study by the World Resources Institute
(WRI) Indias energy demand is expected to more
than double by 2030. The country is consequently
in need of a huge amount of new power generation
capacity. Considering the figures of the WRI,
the cheapest generating capacity for India will
no doubt be energy savings.

Per Capita Energy Consumption in Some

Countries (kWh). How does it compare?

631
1379
Canada

6206
17179

USA
Japan
UK

8076

China
13338

India

India - Primary Energy Sources in India(%)

9%

6% 1%

Coal
Oil

31%

53%

Gas
Hydro
Nuclear

Source :BP Statistical Review of World Energy, June 2009

India - Estimated Fuel Mix by 2020 (%)

16
30
5

Coal
Oil
Gas

Renewable
Nuclear
Traditional
16
25

Source : World Energy Statistics, 2009

India Potential for various Renewable Energy Technologies by 2020

Sources/System

Approximate Potential

Biogas plants (in millions)

12

Improved woodstoves in
millions)
Biogas (MW)

120

Solar Energy (MW/KM2 )

20

Wind Energy (MW)

20000

Small Hydropower (MW)

10000

Ocean Energy (MW)

50000

17000

Source: India 2020 A Vision for the New Millennium by Dr. A P J Abdul Kalam & Y S Rajan, Page No. 254

Definitions of Energy terms

 Primary energy carriers are substances which have not yet

undergone any technical conversion,
whereby the term primary energy refers to the energy content
of the primary energy carriers and the "primary" energy flows
Secondary energy carriers are energy carriers that are
produced from primary or other secondary energy carriers,
either directly or by one or several technical conversion
processes (e.g. gasoline, heating oil, electrical energy),
whereby the term secondary energy refers to the energy
content of the secondary energy carrier and the corresponding
energy flow

 Final energy carrier and final energy respectively are

energy streams directly consumed by the final user (e.g.
light fuel oil inside the oil tank of the house owner, wood
chips in front of the combustion oven, district heating at
the building substation)
Useful energy refers to the energy available to the
consumer after the last conversion step to satisfy the
respective requirements or energy demands (e.g. space
heating, food preparation, information, transportation).
It is produced from final energy carrier or final energy,
reduced by losses of this last conversion (e.g. losses due
to heat dissipation by a light bulb to generate light,
losses of wood chip fired stove to provide heat)

 Fossil energy resources are stocks of energy that have

formed during ancient geologic ages by biologic and/or
geologic processes.
They are further subdivided into fossil biogenous
energy resources (i.e. stocks of energy carrier of
biological origin) and fossil mineral energy resources
(i.e. stocks of energy carrier of mineral origin or nonbiological origin).
The former include among others hard coal, natural
gas and crude oil deposits, whereas the latter comprise
for instance the energy contents of uranium deposits
and resources to be used for nuclear fusion processes.

 Conventional energy :Energy that has been used from

ancient times is known as conventional energy. Coal,
natural gas, oil, and firewood are examples of
conventional energy sources. Basically A Fossil Fuel.
Non conventional energy sources are those energy
sources which are exposed to use from modern
technological advancements; rather than the normal
use of conventional fuels as energy sources like gas or
oil.
E.g. tidal energy, geothermal energy etc can be
harnessed
now with new technology.

Renewable energy
These are the resources that can be generated
continuously.
Renewable energy is natural energy which does not have a
limited supply. Renewable energy can be used again and
again, and will never run out.
Renewable energy includes conventional energy sources
like: firewood, petrol plants, plant biomass, animal dung,
water energy etc. These are mostly biomass based which
are renewed over relatively short period of time and then
available in unlimited amount in nature.
Non-conventional energy sources like solar energy, wind
energy, tidal energy, geothermal energy and hydro thermal
energy etc. These can reproduce themselves in nature and
can be harvested continuously through a sustained
planning and proper management

 Non- renewable or exhaustible energy

sources: These are available in limited amount
and develop over a longer period of time.
Hence, they cannot be replenished in the
quantities they are being consumed in a given
period of time.
This include Conventional sources like coal,
petroleum etc and Non- Conventional energy
sources like nuclear energy etc.

Why should we look for alternate energy

sources?
Fossil fuels, which are the main source of
energy, are getting depleted at a rapid rate. As
a consequence the cost of fossil fuels are
increasing.
Fossil fuel based systems produce detrimental
effects on the environments. This in turn will
affect our health. This means that indirectly,
the medical bills will be rising the world over.

How long will fossil fuel last?

 Consider a hypothetical case where in earth contains a

thin core filled entirely with oil as shown in the previous
slide. It turns out that the volume of the oil present is
1.0861021m3((4/3)(6378103)3).

The energy density of fuel is in the range of

10000Wh/Lt.
The energy content in the fuel within the earth is
obtained as 1.11025KWh. Assuming that growth rate is
maintained at 7% and the entire energy is supplied
using fossil fuels.

 The energy requirement at any time, t can be

calculated using 701012e0.07tKWh

t is obtained as 368 years. The fossil fuels will

get depleted in about 368 years.

 If we consider the real situation, the earth is notcompletely filled with oil as assumed and further
the annual energy consumption rate is continually
growing. So the fuel may get exhausted in about
70-100 years.
If the reserves of fuels decrease there will be a
sharp increase in the price of energy. This will
lead to decrease in energy consumption through
fossil fuels. If alternative sources are explored and
utilized, then the fuel may be actually used for
more number of years.

ENERGY for the future - Some Options

Clean Coal Technologies
Usage of renewable energy resource
Modernization of power transmission & distribution
system
Alternative fuels for surface transportation- bio-fuels,
electric vehicles, hydrogen and fuel cell vehicles.
Hydrogen has significant potential as a clean energy
source

What is Conventional/ non conventional?

Conventional energy :Energy that
has been used from ancient times
is known as conventional energy.

Coal, natural gas, oil, and firewood are

examples of conventional energy
sources. Basically A Fossil Fuel.

Non conventional energy sources are those

energy sources which are exposed to use
from modern technological advancements;
rather than the normal use of conventional
fuels

E.g. tidal energy, geothermal energy

Fossil fuels
Fossils fuels (oil, coal, natural gas) are energy rich
substances that have formed from the remains of
organisms that lived 200 to 500 million years ago.
During the stage of the Earths evolution, large
amount of dead organic matter had collected.
Over million of years, this matter was buried
under layers of sediment and converted by heat
and pressure into coal, oil and natural gas.
Coal is mostly used in the generation of electricity
(thermal power).
Natural gas is used for commercial and domestic
purposes like heating, air conditioning and as
fuels for stoves and for other heating appliances.

 Chemically, fossil fuels largely consist of hydrocarbons,

which are compounds of hydrogen and carbon. Some
fossils fuel also contains smaller quantities of other
compounds.
Majority of fossil fuels are being used in transportation,
industries heating and generation of electricity.
Crude petroleum is refined into gasoline; diesel and jet
fuel that power the worlds transportation system.
Today, fossil fuels are considered to be non-renewable for
the reason that their consumption rate is far in excess of
the rate of their formation.

Oil
Crude oil, also called petroleum, is a thick liquid
found in underground rock formations.
The petroleum industry extracts crude oil out of the
ground and then refines it into products such as
gasoline.
Crude oil contains a complex mixture of compounds
made of carbon chains with hydrogen molecules
attached to each link in the chain.

Oil
Extracted crude oil also contains small amounts of
sulfur, oxygen, and nitrogen compounds mixed
with the hydrocarbons.
The principle of oil refining is to remove crude oils
impurities, that is, anything that is not a
hydrocarbon.
The following nations hold the largest oil reserves,
in order:
Saudi Arabia, Canada, Iran, Iraq, United Arab
Emirates, Kuwait, Venezuela, Russia, Libya, and
Nigeria.

Coals
about 250 to 350 million years ago coal was formed on
earth in hot, damped regions.
Almost 27350 billion metric tones of known coal
deposits occur on our planet. Out of which about 56%
are located in Russia, 28% in USA and Canada.
India has about 5% of worlds coal reserve and that too
not of vary good quality in term of heat capacity.
West Bengal, Jharkhand, Orissa, Andhra Pradesh,
Madya Pradesh and Maharastra are the major coal
producing states of India.

Mainly, there are three types of coal:

Anthracite or hard coal ( 90% carbon content)
Bituminous or soft coal (85% carbon content)
Lignite or brown coal (70% carbon content)
The present annual extraction rate of coal is
about 3000 million metric tones, at this rate
coal reserves may lasts for about 200 hundred
years and if its use is increased by 2% per year
then it will last for another 65 years.

Advantages and Disadvantage of Coal

Advantage

Disadvantage

Ample supplies (225- Very high environmental impact

900years)
High net energy yield High land use (including mining)
Low cost (with huge
substitutes)

Severe threat to human health

Mining and
combustion
technology well
developed

High carbon dioxide emissions when

burnt

Petroleum
Convenience of petroleum or mineral oil and its greater
energy content as compared to coal on weight basis
has made it the lifeline of global economy.

Petroleum is cleaner fuel when compared to wood or

coal as it burns completely and leaves no residue.
Petroleum is unevenly distributed like any other
mineral. There are 13 countries in the world having
67% of the petroleum reserves which together form the
OPEC (Organisation of petroleum exporting countries)

Petroleum
Six regions in the world are rich in petroleum USA,
Mexico, Russia and West Asian countries. Saudi Arabia
oil producing has one fourth of the world oil reserves.

The oil bearing potential of India is estimated to be

above one million square kilometers is about one third
of the total geographic area.
Northern plains in the Ganga-Brahmaputra valley, the
coastal strips together with their off-shore continental
shelf (Bombay High), the plains of Gujarat, the Thar
Desert and the area around Andaman and Nicobar
Islands.

Advantage

Disadvantageof conventional oil

Advantages and Disadvantage

Amply supply for 40-50years

Need to find substitute within

High net energy yield

Artificially low price encourages waste

and discourages search for alternative

Low cost (with huge substitutes)

Air pollution when burnt,

Releases carbon dioxide

Easily transported within and

between countries , Efficient
distribution system

Moderate water pollution

Low land use

Technology is well developed

Natural Gas
Natural gas mainly consists of Methane (CH4) along
with other inflammable gases like Ethane and propane.
Natural gas is least polluting due to its low Sulphur
content and hence is clearest source of energy.
It is used both for domestic and industrial purposes.
Natural gas is used as a fuel in thermal plants for
generating electricity, as a source of hydrogen gas in
fertilizing industry and as a source of carbon in tyre
industry

Natural Gas
The total natural gas reserves of the world is
about 600 000 billion meters, out of this Russia
has 34%, Middle East 18%, North America 17%,
Africa and Europe 9% each and Asia 6%.
Annual production of natural gas is about 1250
billion cubic meters and hence it is expected to
last for about 50-100 years.
In India gas reserves are found in Tripura,
Jaisalmer, off shore areas of Bombay and KrishnaGodavari Delta.

Advantages and Disadvantage of conventional Natural Gas

Advantage

Disadvantage

Amply supply for 125 years

Non renewable resources

High net energy yield

Methane ( a green house gas) can leak

from pipelines

Low cost (with huge substitutes)

Air pollution when burnt,

Releases carbon dioxide

Less air pollution than other fossil

fuels

Shipped across ocean as highly explosive

LNG

Moderate environmental impact

Sometimes burnt off and wasted at wells

because of low prices

Easily transported by pipelines

Requires pipelines

Low land use

Environmental effects of Using Fossil Fuels:

Acid rain: When fossil fuels are buried, Sulphur,
Nitrogen and Carbon combine with oxygen to form
compounds known as oxide. These oxides when
released into the atmosphere, they react with water
form and result in the formation of Sulphuric acid,
Nitric acid and Carbonic acid. These acids can harm
biological quality of forests, soils, lakes and streams.
Ash particles: Ash particles are the un burnt fuel
particles. However with strict imposition of
Government regulations, some equipments are
provided to trap these particles. Petro and natural gas
generate less ash particles than coal, diesel or gasoline.

Environmental effects of Using Fossil Fuels:

Global warming: Carbon dioxide is a major by product
of fossil combustion and this gas is known as green
hour gas. Green hour gas absorbs solar heat reflected
off the earths surface and retains this heat, keeping
the Earth warm and habituate for living organisms.
Rapid industrialization between 19th and 20th
centuries, however has resulted in increasing fossils
fuel emissions, raining the percentage of carbon
dioxide by about 28%. This drastic increase has led to
global warming that could cause environmental
problems, including disrupted weather patterns and
polar ice cap melting.

Nuclear Energy
Nuclear energy is non- renewable source of
energy,
which
is
released
during
fission(disintegration) or fusion (union) of
selected radioactive materials.
Nuclear power appears to be the only hope for
large scale energy requirements when fossil fuels
are exhausted. The reserves of nuclear fuels is
about ten times more than fossil fuels and its
major advantage is that even small quantities can
produce enormous amounts of energy.

Nuclear Energy
For example, a ton of uranium 235 can
produce an energy equivalent 3 million tones
of coal or 12 million barrels of oil.

Nuclear energy has been successfully used in

the generation of electricity in spaceships,
marine vessels, chemical and food-processing
industry.

Definitions
Fuels are substances which, when heated,
undergo chemical reaction with an oxidizer,
typically oxygen, to liberate heat.
Commercially important fuels contain carbon
and hydrogen and their compounds, which
provide heating value

Definitions (contd)
Fuels may be solid, liquid or gaseous
Fuels may be fossil (non-renewable) or
biomass (renewable)
Fossil fuels may be coal, petroleum-crude
derived or natural gas.
Biomass fuels may be wood, refuse or
agricultural residues.

Definitions (contd)
World-wide production of fossil fuels in 1994:
Coal: 180 x 1015 kJ
Petroleum crude: 114 x 1015 kJ
Natural gas: 98 x 1015 kJ
Biomass fuels provide about 20 x 1015 kJ to world
energy production
Fossil fuels provide about 85% of world energy
production. Balance provided by hydroelectric,
nuclear and biomass.

Some statistics
Middle East and Eastern Europe have 70% of
worlds natural gas reserves
Middle East has 67% of worlds crude oil
reserves
Canada has approx. 1 trillion barrels of oil in tar
sands
North America, Eastern Europe and China have
the largest coal reserves

Some statistics
The US with a small fraction of the worlds population
consumes 25% of the worlds crude oil, 25% of the
worlds natural gas and 21% of the worlds coal
production. They also have a third of the worlds
motor vehicles
Each American uses the same energy as 3 Japanese,
38 Indians and 531 Ethiopians!

LIQUID FUELS

1. Occurrence and Processing

The basic source of liquid fuels is crude oil,
which occurs in strata of sedimentary rocks.
Gaseous, liquid and semi-solid materials are
separated at the well head, but the liquid
fuels which are burned in practice are first
processed in a refinery.

88

 The most significant of the refinery processes

is distillation.
The crude oil is flashed (i.e. it undergoes a
sudden drop in pressure) into a column.
The main part of the column is at atmospheric
pressure with a vacuum section producing the
heavier products.

89

 The vaporized oil travels up the column which

has a vertical temperature gradient with the
top of the column being the coolest part (Fig.
8.1, next slide).
The fraction of the oil which vaporizes in the
column will condense out at the appropriate
level in the column.
A system of bubble caps and trays is used to
facilitate this.
90

 All the products which have been condensed

in the column are grouped as distillate oils,
whereas the component of the feedstock
which did not evaporate forms residual fuel
products.
Further processing will take place which
enables heavier fractions to be cracked into
lighter products or the lower molecular weight
components reformed into larger molecules.
93

2. Properties of oil Fuels

Table 8.1 (next slide) gives some physical
properties of the commercially important fuel
oils.
Some explanatory notes about the properties
in the table follow.

94

 Flash Point
This gives an indication of the flammability of
the fuel.
Its significance is in the safety aspects of
storing and handling the fuel.
Viscosity
This is a measure of resistance to flow.
It reflects the energy required to pump the oil
through pipework and it has an important
bearing on the atomization process in burners.
96

 The usual method of quoting the viscosity of

an oil is to give the value of the kinematic
viscosity in centistokes (cs).
Kinematic viscosity is the dynamic viscosity
divided by the density of the fluid.
It is measured in a standard U-tube
viscometer at 38.

97

 Pour Point
This is complementary to viscosity in that it
gives an indication of the temperature at
which the oil will start to flow freely.
Calorific Value
The calorific value of a liquid fuel is measured
in a bomb calorimeter, which measure directly
the gross calorific value at constant volume.
It can be seen that the less volatile oils have
lower calorific values.
98

 Sulfur content
Sulfur exists in all liquid fuels, but it is present
to a significant degree in residual fuel oils.
When burnt, sulfur forms SO2 and SO3 which
are major sources of air pollution.

99

 There are two important consequence of SOX

for thermal plant installations:
The flue must be designed to provide acceptable
concentrations of SOX at ground level;
It is particularly important to prevent
condensation from the flue gases anywhere in
the equipment, as both SO2 and SO3 are
soluble in water, forming sulfurous and sulfuric
acid respectively, and sulfuric acid vapor can
be formed in the flue gas.
100

 Specific Heat
A knowledge of the specific heat of the liquid
is important in handling liquid fuels since the
residual oils all have to be heated before they
can be atomized, and the heavier grades must
be stored in a heated tank if they are to flow
freely into the distribution pipework.

101

 Relative Cost
Although there is a clear price differential in
favor of the residual oils, the capital
investment in the storage system, handling
and combustion equipment for residual fuel
oils is significantly higher than that needed for
distillate oils.

102

3. Combustion of Liquid Fuels

For efficient combustion, a liquid fuel must be
broken up into a stream of droplets to
maximize the surface area-to-volume ratio.
The various types of burner accomplish this in
different ways, but the objective of all types of
burner is to produce a spray of droplets which
are small, and which have a narrow size
distribution.
103

 The combustion process consists of

evaporation of the droplet, driven by heat
transfer from its surroundings, with the vapor
subsequently burning in a diffusion flame.
A classical analysis of this situation where the
heat transfer to the droplet is by convection
shows that the rate of mass transfer (and
hence the combustion rate of the droplet) is
inversely proportional to the diameter.
104

 Because evaporation of the droplet is the

controlling influence on the combustion rate,
liquids with low latent heats of evaporation
will burn more quickly.
The combustion of a liquid fuel spray is more
complex than is indicated above: in particular,
heat transfer to the droplet will be by
radiation as well as convection.
105

 The combustion of oil is a two phase process.

Intimate mixing of the fuel and air is an
important requirement hence the fuel is
broken up into a fine spray, or atomized.
Three common oil burners with different
atomization methods are reviewed below.

106

4. Pressure Jet Burners

The simplest form of pressure jet consists of a
swirl chamber through which the fuel passes
before issuing through the final orifice (Fig. 8.2,
next slide).
Angular velocity is imparted to the liquid by
tangential slots or ports.

107

 The fuel emerges from the jet as a conical

sheet which subsequently breaks up into
droplets of between 10 and 200 m diameter.
The oil supply pressure is usually greater than
500 kPa.

110

 The simplest and most common type of oil

burner incorporates the pressure jet, and this
is shown diagrammatically in Fig. 8.3 (next
slide).
Pressure jet burners span a wide range of
ratings, from domestic units of about 25 kW
up to 2.5 MW.
Classes C, D, and E oils can be burned.
111

 The control of the output of the burner

depends on its size.
Units of less than 300 kW usually operate in
on/off mode; larger units than this can
incorporate continuous modulation of the air
and oil supply flow rates, with reversion to
on/off control at low loads.

113

 Pressure jet burners are not capable of

modulating to accommodate a wide range of
loads.
A maximum turndown ratio (max. firing
rate/min. firing rate) of 2:1 can be achieved,
but 1.5:1 is a more usual figure.

114

5. Rotary Cup Burners

The supply of oil is fed onto a rotating surface
(usually a cup or disk) and the atomization is
achieved when the fluid is flung off the cup by
centrifugal force (Fig. 8.4, next slide).

115

 These atomizers tend to give a narrow size

range of droplets and are ideally suited to the
more viscous liquid fuels, as pumping
pressures are much lower than those for
pressure jet burners.
The cup rotates at 4,000-6,000 rpm to atomize
a class G residual fuel oil, although much
higher speeds are used in some applications.
118

 The air supply to this type of burner is split

into two streams: 15% is supplied as primary
air around the atomizer itself, the remainder
being admitted subsequently as secondary air.
Rotary cup atomizers are used to burn residual
oils of classes E, F and G, and are rated
between 150 kW and 5 MW.

119

6. Twin-fluid Atomizers
A second fluid (typically air or steam) is used
to produce the shear necessary to break up
the oil into droplets.
The nozzle is essentially similar to that of the
pressure jet burner with the addition of an
extra set of tangential ports on the inside or
outside of the oil flow passage.

120

 In an air-blast atomizer about 2-10% of the

combustion air is supplied at a high pressure
(20-100 kPa).
This type of atomizer is more expensive to
operate than the other types but it is capable
of much greater load modulation, achieving
turndown ratios up to 5:1, which can make
the extra expense worthwhile.
121

7. Storage of Liquid Fuels

Tanks may be located inside or outside and
are usually of the vertical or horizontal
cylindrical type.
It is usual to allow for a storage capacity
equivalent to 2-3 weeks full load running this figure is easily obtained from the rating of
the burner and the calorific value of the fuel.

122

 The oil tank itself must be vented and a bund wall

must be provided which can hold the entire tank
contents.
For distillate oil systems a single pipe system is
adequate for delivery of the oil to the burner.
For residual fuel oil systems a ring main system is
required and provision must be made to ensure
that the oil is at the appropriate temperature, as
summarized in Table 8.2 (next slide).
123

Table 8.2 Storage and handling temperatures for liquid fuels

Class
E
F
G

124

Min. temperature ()
Storage

Outflow

10
25
40

10
30
50

 Additional heating is usually provided at the

burner appropriate to the type of atomizer in
use.
Where storage heating is required (classes F
and G) the tank is insulated against heat loss.

125

Types of Fuels
Liquid Hydrocarbon fuels may be
1. Paraffins: straight chain compounds like methane, ethane,
propane, etc. or branched chain compounds (isomers) like
iso-butane, iso-heptane (like 2,2,3 tri-methyl butane or
triptane) and iso-octane (like 2,2,4 tri-methyl pentane).
2. Olefins: Open chain unsaturated hydrocarbons with a
double bond like ethene or propylene which also have
straight and branched chain compounds.
3. Diolefins: These are olefins with 2 double bonds.
Both types of olefins produce gum when reacted with oxygen
which can block fuel filters.

Types of Fuels (Continued)

4.

Alkynes: Unsaturated hydrocarbons with a triple bond. A

typical example is acetylene or ethyne.
5. Napthenes or Cycloparaffins: Have same general formula as
monoolefins but are saturated compounds with a ring
structure. Examples are cyclopropane, cyclobutane etc.
6. Aromatics: Ring structured unsaturated hydrocarbons with
double bonds but more stable than the parafffinc double
bond hydrocarbons. Examples are benzene, toluene,
naphthalenes, and anthracenes.
The molecular weight of a hydrocarbon is given by:
Mol. Wt.=12x + y
where x = carbon no. & y = no. of H atoms

Gasoline from Methanol

Gasoline from Methanol

General Formulas for Organic

Compounds found in Crude Oil
Family

Formula

Structure

Paraffins (alkane)

CnH2n+2

Straight and
Branched

Paraffins (alkene)

CnH2n

Paraffins (alkyne)

CnH2n-2

Naphthenes
(cyclanes)

CnH2n

Straight and
Branched
Straight and
Branched
Ring

Aromatics
(Benzenes)

CnH2n-6

Ring

Aromatics
(naphthalene)

CnH2n-12

Ring

Differences Between Coal and

Petroleum
Coal

Petroleum

Formed from land plants

decaying under mildly
reducing conditions

Formed mainly from sea

plants and animals decaying
under strongly reducing
conditions

Seams remain where

Can migrate under effects of
deposited, i.e., location of
temperature and pressure,
existing deposits are usually
i.e., location of existing
same as the location of
deposits may not be the
accumulation of debris
same as location of
accumulation of debris

Composition of typical crude oil

Carbon:
80-89%
Hydrogen:
12-14%
Nitrogen:
0.3-1.0%
Sulfur:
0.3-3.0%
Oxygen:
2.0-3.0%
Plus oxygenated compounds like phenols, fatty
acids, ketones and metallic elements like
vanadium and nickel.

Typical Refinery Products

Product
Liquefied Petroleum Gas

Boiling Range, oC
-40 to 0

Motor Gasoline

30-200
170-270
180-340
180-340
340-540
340-650
540+
Solid

Kerosene, jet fuel (ATF)

Diesel Fuel
Furnace Oil
Lube Oils
Residual Fuel
Asphalt
Petroleum Coke

Products from Asphalt-based Crude

Products from Paraffin-based Crude

Refinery processes
1. Distillation: Continuous, Atmospheric, and
Vacuum.
2. Cracking: Thermal, Catalytic and Hydro.
3. Reforming: Thermal, Catalytic and Hydro
4. Polymerization
5. Alkylation
6. Isomerization
7. Hydrogenation

Likely Fuels from Various Primary Energy Resources

with Conversion Efficiencies
Primary Energy Resource
(Conversion Efficiency)

Fuels Obtainable

Petroleum Crude
(0.90-0.98)

Cleaned crude oil (water, solids,

and gases removed. Distillate fuel
(obtained from distillation)

Oil Shale
(0.63-75)

Hydrogenated shale oil. Distillate

fuel.

Coal
(0.37-0.95)

Powdered coal. Pulverized coal.

Solvent refined coal. Distillate fuel.
Fischer-Tropsch liquid HCs

Biomass
(0.25-0.35)

Ethanol. Liquid hydrocarbons.

Nuclear
(0.17-0.20)

Methanol, Fischer-Tropsch liquid

hydrocarbons

Petroleum Crude Conversion to Oil

Coal Conversion to Oil

Oil Shale Conversion to Oil

Liquid fuels
Liquid fuels are derived from 2 main sources :
From crude oil and from coal.
Liquid fuels can be divided into 2 classes,
Light oils /spirits, suitable for IC engines
Heavy oils, suitable mainly for burning in
furnaces.

Petroleum
The approximate composition of petroleum is:
carbon 80-89%, hydrogen 12-14%, nitrogen 0.31.0%, sulphur 0.3-3.0% and oxygen 2-3%.
Chemistry of petroleum: The main components
of petroleum are hydrocarbons i.e, they contain
only carbon and hydrogen. Carbon combines with
hydrogen in various amounts to form a variety of
compounds. Types of hydrocarbons found in
petroleum are paraffins, iso-paraffins, olefins,
naphthenes, and aromatics.

Paraffins:
They are given the suffix ane,eg.,methane,
ethane propane etc.Their general formula is
CnH2n+2.These compounds are quite stable and
have a lower specific gravity.The compounds
with lower molecular weight are gasses at room
temperature and pressure

Iso-paraffins:
Iso-paraffins are isomers of normal
paraffins.The chemical formula remains the
same but the arrengement of atoms is
modified.
Eg.,2,2,4-trimethylpentane.
Pentane indicates the five carbonatoms of a
paraffin molecule,trimethyl indicates 3 methyl
groups attached to main carbon chain,2,2,4
gives the number of carbon atoms in the main
chain to which the methyl group is attached.

Olefins:
olefins are generally named with the
suffixene,eg., pentene, octene etc.They have
a straight carbon chain but with one or more
carbon atoms doubly bonded together. They
are unsaturated hydrocarbons. They are
chemically active as compared to the other
hydrocarbons and have good burning
characteristics.

Naphthenes:
Naphthenes are designated by the
termcyclo in their name because of the
carbon ring in the molecule.They have general
formula as for monolefins but they are
saturated( CnH2n).

Aromatics:
Aromatics are those that have benzene rinfg
in their molecular sructure.The banzene ring
consists of 6 carbon atoms in a ring with
alternative carbon atoms double bonded.This
leaves the carbon atom with a single
valence.An aromatic which has a single
hydrogen atom in the benzene ring replaced
by a normal alkyl group is called an
alkylbenzene
compound,
eg.,n-propylbengene.

Fractional Distillation

Distillation is a process of separation on a

molecular basis. The crude oil is first heated
around 300c to 350c. These vapors are then
condensed in a cylindrical tower called
FRACTIONATING COLUMN. The column is kept
at nearly atmospheric pressure.
The
uncondensed gases leave the tower from the
top, and are sent for absorption.
Substances with high boiling points condense
at the bottom and substances with low boiling
points condense at the top.

Cracking
Cracking means the breaking of heavy molecules
into lighter hydrocarbons. In this process, the
temperature is around 500c. At this elevated
temperature, heavy oils decompose to give lower
hydrocarbons which have a low boiling range and
a heavy residue of coke.
The cracking process is two types:
thermal
catalytic.

Thermal Cracking

Initiation reactions, where a single molecule breaks apart into two free radicals. Only a
small fraction of the feed molecules actually undergo initiation, but these reactions are
necessary to produce the free radicals that drive the rest of the reactions. In steam
cracking, initiation usually involves breaking a chemical bond between two carbon atoms,
rather than the bond between a carbon and a hydrogen atom..
CH3CH3 2 CH3
Hydrogen abstraction occurs where a free radical removes a hydrogen atom from another
molecule, turning the second molecule into a free radical.
CH3 + CH3CH3 CH4 + CH3CH2
Radical decomposition occurs where a free radical breaks apart into two molecules, one an
alkene, the other a free radical. This is the process that results in the alkene products of
steam cracking.
CH3CH2 CH2=CH2 + H
Radical addition, the reverse of radical decomposition, occurs where a radical reacts with
an alkene to form a single, larger free radical. These processes are involved in forming the
aromatic products that result when heavier feedstocks are used.
CH3CH2 + CH2=CH2 CH3CH2CH2CH2
Termination reactions occur when two free radicals react with each other to produce
products that are not free radicals. Two common forms of termination are recombination,
where the two radicals combine to form one larger molecule, and disproportionation,
where one radical transfers a hydrogen atom to the other, giving an alkene and an alkane.
CH3 + CH3CH2 CH3CH2CH3 CH3CH2 + CH3CH2 CH2=CH2 + CH3CH3

catalytic cracking
The feedstock to an FCC is usually that portion of the crude oil that has an initial boiling
point of 340 C or higher at atmospheric pressure and an average molecular weight ranging
from about 200 to 600 or higher. This portion of crude oil is often referred to as heavy gas
oil. The FCC process vaporizes and breaks the long-chain molecules of the high-boiling
hydrocarbon liquids into much shorter molecules by contacting the feedstock, at high
temperature and moderate pressure, with a fluidized powdered catalyst.

Vacuum Distillation Process

The residue of processes can be refined to
yield more gasoline by vacuum distillation.
Due to high temperature and low pressure,
heavy distillates are squeezed out of the
residue. The remaining residue is called
vacuum bottoms. The distillate is usually
subjected to the catalytic cracking process.
These vacuum bottoms can be used as charge
for the visbreaking process.

 Some compounds have very high boiling points. To

boil such compounds, it is often better to lower the
pressure at which such compounds are boiled instead
of increasing the temperature. Once the pressure is
lowered to the vapor pressure of the compound (at
the given temperature), boiling and the rest of the
distillation process can commence. This technique is
referred to as vacuum distillation and it is commonly
found in the laboratory in the form of the rotary
evaporator.
This technique is also very useful for compounds
which boil beyond their decomposition temperature
at atmospheric pressure and which would therefore
be decomposed by any attempt to boil them under
atmospheric pressure.

Visbreaking

This process is similar to thermal cracking

except that the pressure and temperature
used are lower. The purpose of this process is
to obtain large volumes of distillate for
catalytic cracking from vacuum bottoms.
A visbreaker thermally cracks large
hydrocarbon molecules in the oil by heating
in a furnace to reduce its viscosity and to
produce
small
quantities
of
light
hydrocarbons (LPG and gasoline)

Reforming Process
The purpose of the reforming process is to change the chemical nature of
various hydrocarbons to give the desired physical properties. These
include thermal and catalytic reforming.
The main difference between the refining and reforming processes is
that the former is carried out on crude, residue, or heavy oils, while the
latter is done on gasoline.
Catalytic reforming is a chemical process used to convert petroleum
refinery naphthas, typically having low octane ratings, into high-octane
liquid products called reformates which are components of high-octane
gasoline (also known as petrol). The overall effect is that the product
reformate contains hydrocarbons with more complex molecular shapes
having higher octane values than the hydrocarbons in the naphtha
feedstock. In so doing, the process separates hydrogen atoms from the
hydrocarbon molecules and produces very significant amounts of
byproduct hydrogen gas for use in a number of the other processes
involved in a modern petroleum refinery.

Reforming
Thermal Reforming

Catalytic Reforming

Thermal reforming is similar to

thermal cracking.
The temperature of around
500-600c and pressure of
around 80 kg/cm.
The Extent of reforming is
controlled by quenching the
hot vapours with cold oil called
quenching oil.
The quenched vapours are
then passed in to a fractionate
column to remove residual
gases.

Catalytic reforming is a chemical

process
used
to
convert
petroleum refinery naphthas,
typically having low octane
ratings, into high-octane liquid
products called reformates which
are components of high-octane
gasoline (also known as petrol).
Basically, the process re-arranges
or re-structures the hydrocarbon
molecules in the naphtha feed
stocks as well as breaking some
of the molecules into smaller
molecules

Polymerization
Light
gases resulting from fractional
distillation and cracking can be polymerized
to give heavier hydrocarbons, thus increasing
the yield of gasoline from the escaping gases.
Polymerization is the reverse of cracking.
Ethylene, propylene, butylene, etc. are quite
reactive and can easily be polymerized in the
presence of a catalyst at higher temperatures
and pressures to give liquid hydrocarbons.

Isomerization
The process of changing one type of molecule
to another type with the same molecular
weight is known as isomerization.
It is usually carried out in the presence of a
catalyst aluminium chloride(ALCL3) activated
by anhydrous hydrochloric acid.
The temperature and pressure suitable for
such reactions are 110c and 21kg/cm3 for
butane isomerrization.

Flash point and Fire Point

Flash Point
As fuel oils are heated,
vapours are produced which
at a certain temperature
flash when ignited by an
external
flame.
This
temperature is called the
flash point of the oil.

Fire Point
As fuel oil are heated,
vapours are produced which
at a certain temperature
flash when ignited by an
external flame. If heating is
continued,
sufficient
vapours are finally driven
off to produce continuous
burning and not a single
flash. This temperature is
called the fire point.

Calorific value & Ash Content

Calorific value
The calories or thermal
units contained in one unit
of a substance and released
when the substance is
burned.
The quantity of heat
produced by the complete
combustion of a given mass
of a fuel, usually expressed
in joules per kilogram

Ash Content
Ash is the inorganic residue
remaining after the water
and organic matter have
been removed byheating in
the presence of oxidizing
agents, which provides a
measure of the total
amount of minerals.

Reid vapour pressure

This is a measure of vapour pressure of an oil at 38c

expressed in kg/cm3 or in millimeters of mercury.
The vapour pressure is a measure of tendency of gasoline to
vapour lock or generate vapour bubbles in the oil line.

VARIOUS PETROLEUM PRODUCTS

Motor gasoline
Aviation gasoline
Aviation turbine fuels
Kerosene
Diesel fuels
Fuel oils
Oil shales

Motor gasoline:
Motor gasoline is an ideal fuel for spark ignition engines. The
main advantage of a gasoline engine is its light weight per
B.H.P. developed. This makes it most suitable for automotive
vehicles.

Aviation gasoline:
The desired properties of aviation gasoline are slightly
different than for motor gasoline. Various grades of aviation
are gasolines are available.
The grade number indicates its octane number or
performance number.

Kerosene:
It is extensively used for heating and lighting. Its boiling
range is 150 to 300oc. It mainly consists of paraffins. Its
viscosity should be less than 2.5 centistokes for easy flow of
fuel through capillaries or the wick.

Diesel fuels:
Diesel fuels are used in compression ignition engines. The
normal boiling range for the diesel fuel is 200 to 370oc. High
speed diesel may use oils with initial boiling point as low as
140oc.

SOLID FUELS

1. Introduction
Solid fuel embraces a wide variety of
combustibles, ranging from wood, peat and
lignite, through refuse and other low calorific
value substances, to coal and other solid fuels
derived from it.
Coal represents by far the largest component
of the worlds fossil fuel reserves.

186

 In thermal terms 90% of the known

hydrocarbon fuel deposits are formed by coal.
The carbon: hydrogen ratio of coal is the
highest of the fossil fuels, hence the calorific
values of coals are principally determined by
the carbon in the fuel.

187

 It is usual to consider coals in terms of their

rank: in general, a high ranking coal will have a
high carbon content.
The other major coal constituent element,
hydrogen, is present in hydrocarbons which
are released as volatile matter when the coal
is heated.

188

 Coal is a sedimentary rock of vegetable origin.

Vast deposits of plant material, formed
approximately 80 million years ago, were
consolidated by pressure, heat and earth
movement.
The rank of a coal is related to its geological
age and, generally, its depth in the earth.

189

 The ranking sequence is:

Wood
Peat
Lignite (brown coal)
Bituminous Coal
Anthracite
In general, deposits close to the surface which
can be worked by strip mining produce a more
economical fuel than deep mined coal.
190

 Coal was the fuel which fired the Industrial

Revolution, but it is no longer the cheapest
option among the fossil fuels.
The cost of working the deposits and the
investment in technology needed to meet
increasingly stringent emissions standards
have increased the cost of burning coal.

191

 Recent developments in gasification processes

have shown that it is possible to produce gas
from coal at a viable thermal efficiency and to
remove the sulfur from the fuel at the same
time.

192

2. Coal Classification
As the rank of a coal increases, its carbon
content increases from 75% to about 93% (by
weight), the hydrogen content decreases from
6% to 3%, and the oxygen content decreases
from 20% to 3%.
A useful method for analyzing a coal is the
proximate process.
Proximate analyses of some common fuels are
given in Table 9.1 (next slide).
193

Table 9.1 Composition of some typical solid fuels (% by mass)

Fuel

Carbon

Volatile
matter

Moisture

Ash

Peat
Lignite
Bituminous
Coal
Anthracite

44
57
82

65
50
25

20
15
2

4
4
5

90

194

 The moisture in coal is made up of two

components: surface moisture and inherent
moisture.
The former is affected by the way in which the
coal is stored, and is thus variable.

195

 Coals are also analyzed in terms of their

elemental constituents, giving the ultimate
analysis which was used earlier in
stoichiometric calculations.
Typical ultimate analyses of two types of solid
fuels are given in Table 9.2 (next slide).

196

Table 9.2 Ultimate analyses (% by mass) of some coals

Coal

Carbon

Hydrogen

Oxygen

Nitrogen

Sulfur

Anthracite

94.4

2.9

0.9

1.1

0.7

Bituminous

89.3

5.0

3.4

1.5

0.8

197

3. Coal Properties
There are a number of properties which are
important in identifying the suitability of a
coal for any given application:
Size
Some common size groups, together with
their rather picturesque names, are given in
Table 9.3 (next slide).

198

Table 9.3 Size distribution for coals

Name
Large Cobbles
Cobbles
Trebles
Doubles
Singles

199

Upper limit (mm) Lower limit (mm)

>150
75
100-150
50-100
63-100
38-63
38-63
25-38
25-38
13-18

 Calorific value
The ranking of a coal is not necessarily related
to its calorific value.
Coal fuels generally have a range of values
from 21 to 33 MJ/kg (gross).
The design rating of a coal-fired burner is
usually based on an estimated calorific value
of 26 MJ/kg (6,200 kcal/kg).
200

 Ash Fusion Temperature

The melting point of the ash left after combustion of the
coal is of particular importance in terms of the
combustion and ash disposal equipment.
If the ash fuses it produces a glassy, porous substance
known as clinker (slag).
The combustion equipment will be designed to handle
either clinker or unfused ash, and use of the wrong type
of coal can have dire consequences.

201

 Sulfur Content
Many deep-mined coals have a fairly high sulfur content,
typically around 1.5% by weight.
The same consideration apply to coal-fired installations
as to oil-fired combustion equipment namely that
condensation inside the plant must be avoided and that
the design of the flue must ensure that ground
concentration of sulfur oxides are controlled within
acceptable limits.

202

4. Coal Combustion
Coal combustion is a two-phase process and
the objective of the burner is, as always, to
achieve complete combustion of the fuel with
maximum energy efficiency.
Three common ways of burning solid fuels are
currently in use and are briefly reviewed
below.

203

 Pulverized Fuel
The coal is ground to a very fine size (about 0.08mm or
more than 70% pass through #200 mesh) when it can be
made to behave rather like a liquid if air is blown
upwards through the powder.
The preparation and handling equipment is very
expensive and pulverized fuel installations are generally
only economically viable in very large scale applications,
such as thermal power stations.

204

 The fuel is injected in the form of a conical

spray, inside a swirling conical primary air
supply in a fashion analogous to that for an oil
burner.
Fluidized Bed Combustors (FBC)
The basic principle of operation is that the
coal is mixed with an inert material (e.g. sand)
and the bed is fluidized by an upwards flow
of air (Fig. 9.1, next slide).
205

 Although the fluidization requires more fan power than

the conventional grate combustions (Figs. 9.3 & 9.4),
there are a number of advantages in FBC:
(1) The bed temperature can be kept cooler than in
the case of grate combustion-fluidized bed
temperatures are generally within the range 750950.
This means that ash fushion does not occur and
the low temperatures produce less NOX.

207

 (2) High rates of heat transfer can be attained

between the bed and heat exchanger
tubes immersed in it.
(3) A wide range of fuel types can be burned
efficiently.
(4) additives (such as limestone) can be
used which react with oxides of sulfur
retaining the sulfur in the bed with
consequent reduction in SOX emission.
208

 Grate Combustion
The simplest, and most common, way of burning coal is
by igniting a bed of the fuel on a porous grate which
allows air to rise through the bed, either by buoyancy in
smaller equipment or with fan assistance in the larger,
automatic stokers.
The combustion of a coal on a grate commences with
heat transfer to the raw coal from the adjacent
incandescent fuel.
The first effect that this has is to drive off the volatile
matter from the coal.
209

 The volatiles will then rise through the bed,

partly reacting with the hot carbonaceous
material above it, to burn as a yellow flame
above the bed.
As the combustion process proceeds, the
volatile matter decreases until there is only
the carbonaceous residue left, which burns
with the intense emission of radiation.
210

 As the air enters the fuel bed from below, the

initial reaction is the combustion of the
carbon to carbon dioxide.
In the hot upper region of the gas this is
reduced to carbon monoxide:
CO2 + C 2CO
Which burns in the secondary air above the
bed.
211

 The effect of this is to decrease the

concentration of oxygen from 21% at entry, to
zero at about 100 mm above the grate.
At this point, there is a peak in the carbon
dioxide concentration which falls away as the
reduction to carbon monoxide proceeds (Fig.
9.2, next slide).

212

 Underfeed Stoker
Next slide, Fig. 9.3, coal is fed into the retort
by the action of a screw.
When combustion is completed at the top of
the bed, a residue of ash and clinker remains
which falls to the sides of the retort.

214

 The de-ashing of underfeed stokers is

generally a manual process, although some
manufacturers offer automatic ash-handling
facilities.
Bituminous singles with an ash fushion
temperature of around 1,200 are an
appropriate fuel for this type of device.

216

 Chain Grate Stoker

A diagram of a chain grate boiler is shown in
Fig. 9.4 (next slide).
The coal is supplied by the travelling grate and
the thickness of the bed controlled by the
guillotine door.
The speed of the grate and an air damper
setting control the firing rate.
217

 The fuel for such boilers is usually smalls

(about 13-25 mm) with a high ash fushion
temperature.
The ash falls from the end of the grate into a
pit, from where it can be removed by a
conveyor belt or screw.

219

5. Coal Storage and Handling

Solid fuels are stored in bunkers-normally a
quantity equivalent to 100 hours at peak firing
rate is the target storage capacity, with a
minimum amount of 20 tonnes.
Coal is usually conveyed into storage from the
delivery vehicle by tipping or by pneumatic
conveyance along pipes.

220

Forms of Fuels
Natural Form

Artificial Form

Wood

Wood Charcoal

Peat

Peat Charcoal

Lignite

Lignite Briquettes
Lignite Coke

Hard Coal Sub-bituminous

Hard Coal bituminous
Hard coal anthracite

Coal Briquettes Carbonized

and Uncarbonized
Low, Medium & High Temp.
Coke

Solid Fuel Analysis

Proximate analysis: (ASTM D3172)
Sample of known mass, to determine:
Moisture dried at 105 to 110oC in an oven
Volatile combustible matter heated to
900oC in a covered crucible
Fixed carbon heated to 750oC in an open
crucible
Ash the final residue

Solid Fuel Analysis

Ultimate Analysis: (ASTM D3176)
Provides the major elemental composition of the
fuel, that is usually reported on dry, ash-free basis
Carbon includes organic carbon & carbon from
mineral carbonates
Hydrogen includes organic hydrogen & hydrogen
from moisture & mineral hydrates
Other elements include oxygen, nitrogen, sulfur and
others like chlorine.

Wood
A Renewable Fuel

Typical Proximate Analysis of Wood

compared to Coal
Fuel

Moisture,
%
Bituminous
2.5
Coal
Hard Wood
45.6
wet
Hard Wood
0.0
dry
Southern
52.3
pine wet
Southern
0.0
pine dry

Volatile
Fixed
Matter, % Carbon, %
37.6
52.9

Ash, %
7.0

48.58

5.52

0.3

89.31

10.14

0.56

31.5

15.9

0.29

66.0

33.4

0.6

Typical Ultimate Analysis of Some types

of Wood in %
Type of Wood

Ash

California Red
Wood

53.5

5.9

40.3

0.1

Trace

0.2

Western
Hemlock

50.4

5.8

41.4

0.1

0.1

2.2

Douglas Fir

52.3

6.3

40.5

0.1

Trace

0.8

Pine (Sawdust)

51.8

6.3

41.3

0.1

Trace

0.5

Typical Ultimate Analysis of Some types

of Bark Species in %
Types of Wood

Ash

Western Hemlock

53.0

6.2

39.3

0.0

Trace

1.5

Douglas Fir

51.2

5.2

39.2

0.1

Trace

3.7

Loblolly Pine

56.3

5.6

37.7

0.0

Trace

0.4

Long Leaf Pine

56.4

5.5

37.4

0.0

Trace

0.7

Short Leaf Pine

57.2

5.6

36.1

0.4

Trace

0.7

Flash Pine

56.2

5.4

37.3

0.4

Trace

0.7

Typical Values of Calorific Values in kJ/kg

of Wood Fuels
Wood Variety

Calorific Value, green

Calorific Value, dry

Ash-white

10,300

12,550

Beech

9,165

12,465

Birch Yellow

8,850

12,150

Chestnut

6,125

13,440

Cotton Wood

7,035

13,950

Elm-white

8,350

13,280

Hickory

9,425

14,420

Maple, sugar

9,490

13,000

Maple, red

8,710

13,880

Oak, red

7,860

12,940

Oak, white

9,300

12,930

Willow

5,510

13,650

Wood Storage
Wood fuels undergo losses in net available
energy as storage time increases due to
1. Moisture accumulation with time and
reaches saturation.
2. Loss of volatiles due to evaporation: 15% of
net available energy is lost this way.
The pH of wood is reduced making it acidic
leading to corrosive effects
Last in, first out (LIFO) must be followed.

Wood Combustion
1. Surface undergoes thermal breakdown: vapors,
gases, mists (combustibles) are evolved. Exists up
to 200oC.
2. More gases are evolved. Heat liberation reactions
occur but no flaming. Occurs from 200 to 280oC.
3. Gases continue to evolve and heat is liberated.
Flaming starts. Occurs up to 500oC.
4. Above 500oC all gases and tar are driven off. Pure
carbon (charcoal) remains. Further heating will
result in combustion of charcoal.

Combustion Characteristics of Wood

1. It is easily ignited.
2. Does not burn in large pieces because layers of
semi-fused ash forms on the surface.
3. Produces a long, non-smoky flame when burned in
excess air. With limited air, it burns with a lot of
smoke.
4. As saw dust it burns readily. Saw dust can be made
into binderless briquettes at pressures of up to 8
kg/mm2.

Alternate fuels from Wood

1.

Charcoal:
A carbonized form of wood. Involves the decomposition of
the wood in the absence of air. Three methods are known:
a. An ancient process: in pits.
b. Low temperature carbonization: in metal retorts, at
about 350oC.
c. High temperature carbonization: in retorts, at around
1000-1200oC.
Charcoal is easily ignited. Used as reducing agent for iron ore,
domestic cooking and to manufacture producer gas.

Alternate fuels from Wood

1. Charcoal (Continued)
Typical Ultimate analysis on wet basis with ash:
Carbon:
85.2%
Hydrogen:
2.9%
Oxygen+Nitrogen: 3.5%
Ash:
2.5%
Moisture:
5.9%
Calorific Value:
31,400 kJ/kg

Alternate fuels from Wood

2. Substitute Natural Gas (SNG) and Methanol:
Obtained by gasifying wood to carbon monoxide and
hydrogen after moisture is removed.
Wood has self generating water supply and low ash and
sulfur, making its gasification superior to coal
gasification.
CO and H2 are synthesized to form SNG over a catalyst
or methanol. Methanol can be converted to
gasoline by the MTG process.

Alternate fuels from Wood

3. Producer gas:
In India, producer gas from wood is used as a
fuel. Yield from about 500 kg wood is about
7400 m3 and calorific value is about 5600 kJ/
m3.

Peat
Beginning of Fossilization

Peat
Peat is the first stage in the formation of coal.
It is regarded as the borderline between vegetation (biomass)
and a fossil fuel.
It is a brown, fibrous mass of partially decayed plant material
accumulated in situ under water-logged conditions.
Composition depends on type, depth of deposit and age. The
oldest peats are about 1 million years old.
Peat is believed to have formed from wood. When wood is
subjected to bacterial processes under nearly stagnant water,
the cellulose, lignin and protein are decomposed. Residuals
combine to form dopplerite.

Peat (Continued)
Contains 70-90% dopplerite and 5-30% resins
and waxes.
Wet peat contains 95% moisture.
Reduces to 90% when cut.
Reduces to less than 25% when air dried.
Ash is about 3%.
Calorific value varies between 16,700 and
20,900 kJ/kg.

Peat (Continued) Ultimate Analysis

Element

Moss Peat

Forest Peat

Old Peat

Carbon

51.1

55.5

59.5

Hydrogen

6.1

5.8

5.8

Nitrogen

1.8

1.5

2.3

Sulfur

0.6

0.8

1.0

Oxygen

40.4

36.4

31.4

Peat (Continued) Combustion

Characteristics
1. Its low calorific value and high moisture content
reduces furnace temperature and efficiency of
combustion.
2. Its low bulk density (320 kg/m3) reduces capacity
of furnace and increases storage and handling
capacity due to its high volume.
3. Its friable nature (can be easily crumbled) causes
appreciable loss in handling.
4. It may be used as a powder or may be briquetted
without any binder.

Peat Carbonization
Like wood, it may be carbonized at low temperature in
metal retorts. Yields:
Charcoal: 30%
Gases: 19-30%
Moisture: 30-40%
Tar: 6-7%
Gases used to provide heat for carbonization. Tar yields
was and oil. Moisture yields ammonium sulfate,
calcium acetate and methanol.

Ultimate Analysis of Peat on wet basis

with ash:

Carbon:
84.2%
Hydrogen:
1.9%
Oxygen+Nitrogen: 7.8%
Ash:
3.1%
Moisture:
3.0%
Calorific Value 29,300 kJ/kg

Producer gas from Peat

Gives producer gas at an efficiency of 80-85%. No water needed
as in case of coal. Gives high yield of gas and ammonia.
Typical composition:
Carbon monoxide:
17.%
Hydrogen:
10.9%
Methane:
2.5%
Nitrogen:
55.7%
Carbon dioxide
13.3%
Gas yield:
2550 m3/tonne of peat
Calorific value
4100 kJ/m3
Ammonium Sulfate
55 kg/tonne of peat

Lignite

Lignite
Forms the first phase of fossilization of
vegetable matter.
It is an immature form of coal.
Believed to be between 10 and 40 million years
old.
It is intermediate in composition between peat
and bituminous coal.
Most immature lignites are chemically similar to
most mature peats.

Composition of typical lignites

Carbon:
64.5-78.5%
Oxygen+nitrogen+sulfur
16.5-30%
Water (as mined)
20-75%
Water (dried)
12-20%
Ash
3-30%
Volatile matter
40-50%
Sulfur
1-12%
Calorific value (dry)
20,900-29,300 kJ/kg
Used raw or dried in furnaces
Pulverized and used in mills
May be used in briquetted forms as well

Coal
A Fully Fossilized Fuel

Coal A Heterogeneous Mineral

Consists principally of carbon, hydrogen, and oxygen,
with lesser amounts of sulfur and nitrogen.
Other constituents are the ash-forming inorganic
compounds distributed throughout the coal.
Coal originated through accumulation of wood and
other biomass that was later covered, compacted
and transformed into rock over a period of millions
of years.

Coal Classification
There are a number ways to classify coals.
One way is to Rank the coal. It indicates the degree or extent of
maturation.
It is a qualitative measure of carbon content.
Thus lignites and sub-bituminous are low rank coals
While bituminous and anthracite are high rank coals.
Rank is not synonymous with grade which implies quality.
Low rank coals may not be suitable for some applications as the
higher ranked ones
Although they may be superior to them in other applications

Rank of Coal
1.

2.
3.
4.
5.
6.

With increasing Rank, the following characteristics are

noticed:
Age of coal is increased. This increases with increase in
depth of deposit.
A progressive loss of oxygen, hydrogen and in some cases
sulfur, with a corresponding increase in carbon.
A progressive decrease in equilibrium moisture content.
A progressive loss of volatile matter.
Generally, a progressive increase in calorific value.
In some cases, a progressive increase of ash content.

Proximate Analysis of some typical

anthracite coals

Meta-anthracite

Fixed
Carbon
%
>98

Anthracite

92-98

2-8

To

40700

Semi-anthracite

86-92

6-14

250

36750

Class and group

Volatile Age in Cal.

Matter million value
%
years kJ/kg
<2
180 35820

Proximate Analysis of some typical

bituminous coals
Class and group

Fixed Volatile Age in Calorific

Carbon, Matter, million Value
%
%
years
kJ/kg

Low volatile

78-86

14-22

100

36520

Medium volatile

69-78

22-31

To

-do-

High volatile: A,B,C

<69

>31

180

-do-

Proximate Analysis of some typical subbituminous coals

Class and group

Fixed Volatile Age in Calorific

Carbon, Matter, million Value
%
%
years
kJ/kg

Sub-bituminous A

69-72

28-31

40

36050

Sub-bituminous B

64-69

31-36

To

35000

Sub-bituminous C

<64

>36

100

-do-

Proximate Analysis of some typical

Lignites
Class and group

Fixed Volatile Age in Calorific

Carbon, Matter, million Value
%
%
years
kJ/kg

Lignite A

58-64

36-42

36050

Lignite B

51-57

42-49

To

35000

Lignite C

41-51

49-59

40

-do-

Typical oxygen, water and ash content in

solid fuels
Fuel

Moisture
(ash-free)
%
15-50

Ash
(dry) %

Wood

Oxygen
(dry, ashfree) %
45

Peat

35

90

0.1-10

Lignite

25

30

>5

Bituminous coal

>5

Anthracite coal

>5

Refuse-derived fuel

40

24

10-15

0.-1.0

Ultimate Analysis of some typical

anthracite coals
Fuel

N+S

Ash
%

Moisture
%

Anthracite

93-95

3-4

1-2

1-2

~2

~2

Typical
Anthracite

90.27

3.0

2.32

1.44

2.97

1.0

Typical
Anthracite

93.7

2.0

2.2

Balance (Data not

available)

Ultimate Analysis of some typical

Carbonaceous and Bituminous coals
Fuel Type

Carbonaceous

91-93

4.0-4.5

Data not given

Bituminous

80-91

4.5-6.0

Data not given

Typical Bituminous

82.9

5.7

Sub- Bituminous

75-80

5.0-5.1

Typical Sub-bituminous (dry, ash-free)

78

13

Typical Subbituminous

74.0

5.9

13.01

2.26

4.75

2.1

Typical Subbituminous

73.3

5.1

18.4

9.9

N+S

Ash

Moisture

Data not given

Data not given

Data not given

Ultimate Analysis of Some Typical

Lignite, Peat and Wood
Fuel Type

N+S

Ash

Moisture

Lignite

60-75

5.0-5.7

Typical Lignite

68.8

4.7

25.5

Typical Lignite

68

25

Typical Lignite

56.52

5.72

31.89

1.62

Typical Peat

60.5

5.6

33.8

Typical Peat

55

38

Dry, ash-free

Typical Wood

50

44

Tr

Dry, ash-free

Typical Wood

49.3

6.7

44

Data not given

Data not given

Dry, ash-free
4.25

15.0

Data not given

Data not given

Mineral Elements and Chlorine in Pine

and Bituminous Coals
Element

Pine (Ave. values)

(ppm)

Illinois Coal

(ppm)

Ca

760

>5000

Na

28

200-5000

39

200-5000

Mg

110

200-5000

Mn

97

6-210

Fe

10

>5000

40

10-340

Si

>5000

Al

>5000

Cl

48

200-1000

More on coal
Coal may be banded or non-banded.
A banded coal is not homogeneous but consists of
alternate layers or bands of bright-black, dull-black
and gray vegetal matter. Exists in all types of coal.
Attributed to different kinds of wood and plant
substances in various stages of decay.
Non-banded coals are uniform and compact in
structure.

Co-existence of coal and petroleum

Where coal and petroleum co-exist, increasing
temperature affect in opposite ways.
Coal gradually loses its volatility and goes
deeper whereas petroleum becomes
progressively lighter as it cracks and rises.
Thus the best coals are deeper in the ground
whereas the best petroleum are nearer the
ground level.

Coal Combustion
When heated to progressively higher temperatures in
inert atmosphere (very little oxygen present), coal
decomposes.
Evolves water, tar and gas, and leaves a solid residue
whose composition and properties depend on heat
treatment temperature.
Temperature range in which volatilization proceeds
very rapidly is 350-500oC.
But thermal decomposition begins at a much lower
temperature.
Can be divided into 3 stages.

Stages of Coal Decomposition

1.
2.
3.

Below 200oC decomposition is slow. Release of small quantities of

chemically combined water, oxides of carbon and hydrogen sulfide.
Begins between 350 and 400oC and ends around 550oC. About 75% of
all volatile matter is released, including all the tar.
Termed secondary degasification, is characterized by gradual
elimination of hetero-atoms, and ends when the char is transformed
into a graphitic solid. Principal products include water, oxides of carbon,
hydrogen, methane, and traces of C2 hydrocarbons.
As carbon content increases, active thermal decomposition occurs at
progressively higher temperature.
In this stage, there is progressive aromatization of the char, i.e.,
increasingly large hexagonal carbon platelets.
Where residue is a coke, heat treatment up to 1000oC also leads to
marked increase in mechanical strength.

Solid fuels from Coal

Coal can be used as mined or after treatment.
Coal can be briquetted or converted to coke.
1. Briquetting. Done because:
(i) to convert cheap and waste coal dust to
lump fuel.
(ii) to use coal more effectively on the
grate of furnace, and
(iii) to produce smokeless fuel from fine coal.

Briquetting (Continued)
Briquetting may be done as follows:
1. Without binder for sub-bituminous coal, lignite or peat.
2. With binder like pitch for bituminous, carbonaceous and
anthracite coals.
Other inorganic binders like sodium silicate, magnesium
oxychloride and lime silica may be used.
Cereal binders like starch and ground maize may also be
used.
Inorganic binders are easy to use but will increase the ash
content when burned.

Solid fuels from Coal (Continued)

2. Coke. Formed by the carbonization of coal.
Yields benzole, oils and tar. Gaseous
products include coal gas.
Yield and chemical nature of the products
depend on rank of coal carbonized and
duration of carbonization.

Coke (Continued)
Two commercial processes are available:
1. Low temperature carbonization at about 600oC and
2. High temperature carbonization at temperatures above
900oC.
Coal is heated in retorts. Evolves gases like carbon monoxide,
methane, unsaturated hydrocarbons, and hydrogen.
Tar forms up to about 500-600oC.
Coals for converting to coke must have carbon content from 83
to 90%.
Coke is used in iron and steel industries (metallurgical coke),
foundries, and as a domestic (smokeless) fuel.

Coal Liquefaction
Coal can be converted into a clean liquid fuel by reducing its
molecular weight with a substantial reduction in the C/H
ratio. Four methods are possible:
1. Pyrolysis.
2. Direct Liquefaction. Examples are the SRC (Solvent Refined
Coal), the Synthoil and H-coal processes.
3. Indirect Liquefaction. The Fischer-Tropsch synthesis.
Example is the SASOL process developed in South Africa.
4. Chemical Synthesis.
Liquefaction entails use of large quantities of water and there is
the problem of ash disposal and slag removal plus
elimination of sulfur dioxide emissions if the coal contains
large quantities of sulfur.

 Wood, Peat, Coal, Charcoal, Coke, etc. are few solid

fuels
They supply about 33% of the total energy
requirements globally.
COAL:
Is of plant origin(converted because of the prolonged
action of bacteria, fungi, temperature, and pressure)
It is firm, brittle, sedimentary, Combustible rock
It consists mainly C,H,O with minor proportions of N,S
It occurs in two types
4 mts thick sequence deposits of coal streams
10 to 20 mts and sometimes of even 300mts thick more
isolated deposits.

 Wood contains
Cellulose 45-65%
Lignin 25-35%
Water and proteins in solution 10-15%

These are partially decomposed to humus called

humic acid
It occurs as a thick jelly called dopplerite, which is
present in peat(70-90% resins and waxes 5-30%)

However there is no clear demarcation between them.

Anthracite is the oldest coal from geological perspective. It is a hard coal

composed mainly of carbon with little volatile content and practically no
moisture.
Bituminous coal or black coal is a relatively soft coal containing a tarlike
substance called bitumen. It is of higher quality than lignite coal but of poorer
quality than Anthracite. It was usually formed as a result of high pressure on
lignite.Bituminous coal is an organic sedimentary rock formed by diagenetic
and sub metamorphic compression of peat bog material.
Lignite is the youngest coal from geological perspective. It is a soft coal
composed mainly of volatile matter and moisture content with low fixed
carbon.
Fixed carbon refers to carbon in its free state, not combined with
other elements.
Volatile matter refers to those combustible constituents of coal that
vaporize when coal is heated.

Normally D,E and F coal grades are available to Indian Industry

Heating Value:
The heating value of coal varies from coal field to coal field.

Measurement of Moisture
Determination of moisture is carried
out by placing a sample of powdered raw
coal of size 200-micron size in an uncovered
crucible and it is placed in the oven kept at
108+2 oC along with the lid. Then the
sample is cooled to room temperature and
weighed again. The loss in weight
represents moisture.

Measurement of Volatile Matter

Fresh sample of crushed coal is
weighed, placed in a covered crucible, and
heated in a furnace at 900 + 15 oC. For the
methodologies including that for carbon
and ash, refer to IS 1350 part I:1984, part
III, IV. The sample is cooled and weighed.
Loss of weight represents moisture and
volatile matter. The remainder is coke
(fixed carbon and ash).

Measurement of Carbon and Ash

The cover from the crucible used in the
last test is removed and the crucible is
heated over the Bunsen burner until all the
carbon is burned. The residue is weighed,
which is the incombustible ash. The
difference in weight from the previous
weighing is the fixed carbon. In actual
practice Fixed Carbon or FC derived by
subtracting from 100 the value of moisture,
volatile matter and ash.

 The calorific value of a fuel is the quantity of heat produced by

its combustion - at constant pressure and under "normal"
conditions (i.e. to 0oC and under a pressure of 1,013 mbar).

The combustion process generates water vapor and certain

techniques may be used to recover the quantity of heat contained
in this water vapor by condensing it.
The Higher Calorific Value (or Gross Calorific Value - GCV)
suppose that the water of combustion is entirely condensed and
that the heat contained in the water vapor is recovered.
The Lower Calorific Value (or Net Calorific Value - NCV) suppose
that the products of combustion contains the water vapor and
that the heat in the water vapor is not recovered.

Fuel
Acetone
Alcohol, 96%
Anthracite
Bituminous coal
Butane
Carbon
Charcoal
Coal
Coke
Diesel
Ethanol
Ether
Gasoline
Glycerin
Hydrogen
Lignite
Methane
Oils, vegetable
Peat
Petrol
Petroleum
Propane
Semi anthracite
Sulfur
Tar
Turpentine
Wood (dry)

Higher Calorific Value

(Gross Calorific Value - GCV)
Btu/lb

kJ/kg
29,000
30,000
32,500 - 34,000
17,000 - 23,250
49,510
34,080
29,600
15,000 - 27,000
28,000 - 31,000
44,800
29,700
43,000
47,300
19,000
141,790
16,300
55,530
39,000 - 48,000
13,800 - 20,500
48,000
43,000
50,350
26,700 - 32,500
9,200
36,000
44,000
14,400 - 17,400

14,000 - 14,500
7,300 - 10,000
20,900
12,800
8,000 - 14,000
12,000 - 13,500
19,300
12,800
20,400
61,000
7,000

5,500 - 8,800

11,500 - 14,000

6,200 - 7,500

kJ/m3
Acetylene

56,000

Butane C4H10

133,000

Hydrogen

13,000

Natural gas

43,000

Methane CH4

39,820

Propane C3H8

101,000

Town gas

18,000

Btu/ft3
3200
950 - 1150

2550

kJ/l

Btu/Imp gal

Gas oil

38,000

164,000

Heavy fuel oil

41,200

177,000

Kerosene

35,000

154,000

1 kJ/kg = 1 J/g = 0.4299 Btu/ lbm = 0.23884 kcal/kg

1 Btu/lbm = 2.326 kJ/kg = 0.55 kcal/kg
1 kcal/kg = 4.1868 kJ/kg = 1.8 Btu/lbm
1 dm3 (Liter) = 10-3 m3 = 0.03532 ft3 = 1.308x10-3 yd3
= 0.220 Imp gal (UK) = 0.2642 Gallons (US)

Proximate analysis:
The "proximate" analysis gives moisture content, volatile
content, consisting of gases and vapours driven off during
pyrolysis (when heated to 950 C), the fixed carbon and the ash,
the inorganic residue remaining after combustion in the sample
and the high heating value (HHV) based on the complete
combustion of the sample to carbon dioxide and liquid water.
Proximate analysis is the most often used analysis for
characterizing coals in connection with their utilization.
The proximate analysis determines only the fixed carbon,
volatile matter, moisture and ash percentages. proximate
analysis can be determined with a simple apparatus

Proximate analysis indicates the percentage by weight of

the Fixed Carbon, Volatiles, Ash, and Moisture Content in coal.
The amounts of fixed carbon and volatile combustible matter
directly contribute to the heating value of coal. Fixed carbon acts
as a main heat generator during burning. High volatile matter
content indicates easy ignition of fuel. The ash content is
important in the design of the furnace grate, combustion
volume, pollution control equipment and ash handling systems
of a furnace. A typical proximate analysis of various coal is given
in the Table

Significance of Various Parameters in

Proximate Analysis
Fixed carbon:
Fixed carbon is the solid fuel left in the furnace after volatile matter is distilled off. It
consists mostly of carbon but also contains some hydrogen, oxygen, sulphur and
nitrogen not driven off with the gases. Fixed carbon gives a rough estimate of heating
value of coal
Volatile Matter:
Volatile matters are the methane, hydrocarbons, hydrogen and carbon monoxide, and
incombustible gases like carbon dioxide and nitrogen found in coal. Thus the volatile
matter is an index of the gaseous fuels present. Typical range of volatile matter is 20 to
35%.
Volatile Matter
Proportionately increases flame length, and helps in easier ignition of coal.
Sets minimum limit on the furnace height and volume.
Influences secondary air requirement and distribution aspects.
Influences secondary oil support

Ash Content:
Ash is an impurity that will not burn. Typical range is 5 to 40%
Ash
Reduces handling and burning capacity.
Increases handling costs.
Affects combustion efficiency and boiler efficiency
Causes clinkering and slagging.

Moisture Content:
Moisture in coal must be transported, handled and stored. Since it replaces combustible
matter, it decreases the heat content per kg of coal. Typical range is 0.5 to 10%
Moisture
Increases heat loss, due to evaporation and superheating of vapour
Helps, to a limit, in binding fines.
Aids radiation heat transfer.
Sulphur Content:
Typical range is 0.5 to 0.8% normally.
Sulphur
Affects clinkering and slagging tendencies
Corrodes chimney and other equipment such as air heaters and economisers
Limits exit flue gas temperature.

Ultimate Analysis:
The "ultimate" analysis" gives the composition of the
biomass in wt% of carbon, hydrogen and oxygen (the major
components) as well as sulfur and nitrogen (if any).
The carbon determination includes that present in the
organic coal substance and any originally present as mineral
carbonate. The hydrogen determination includes that in the
organic materials in coal and in all water associated with the
coal. All nitrogen determined is assumed to be part of the
organic materials in coal.
The ultimate analysis determines all coal component
elements, solid or gaseous. The ultimate analysis is determined
in a properly equipped laboratory by a skilled chemist

The ultimate analysis indicates the various elemental chemical

constituents such as Carbon, Hydrogen, Oxygen, Sulphur, etc. It
is useful in determining the quantity of air required for
combustion and the volume and composition of the
combustion gases. This information is required for the
calculation of flame temperature and the flue duct design etc.
Typical ultimate analyses of various coals are given in the Table

The above equation is valid for coal containing greater than 15% Moisture content

 SWELLING AND CAKING TEST: ASTM D-720

1gm of air dried coal, freshly ground to pass a 72
mesh is rapidly heated in a crucible above a burner
flame, to 820o C
After the flame from the burning the volatile matter
has dried out or after 24 minutes, which ever is
greater period of time the crucible is cooled. the coke
button is opened is removed and compared with
standard numbered profiles from 1-9 in half minute.
The result is recorded as swelling number or free
swelling Index.

Ash Fusibility test: ASTM D-1857

Molded cone( with dextrin binders) of ash is heated
gradually (800-900o C for 1 hour) in a controlled, mildly,
reducing or/and where desired, oxidizing atmosphere. It is
done to provide information on fusion characteristics of ash.
The deformation temperature is the temperature at which
the tip rounds(Initial deformation temperature),
softenning temperature (temp at which cone has fused
down to a spherical lump, Height=width of base)
The hemisphere temperature (point at which Height is onehalf the width of the base) is the temperature at which the
specimen subsides to a hemispherical lump.
Fluid temperature (temp at which fluid mass has spread out
in a nearly flatter layer with a max height of J6 inches)
It gives the approximation the temperature at which ash
remains after combustion of coal will sinter(solid ash
partilcles weld together without melting), melt and flow.

Agglutinating index
This is determined by mixing the coal with an
inert material such as graded sand and
stating the proportion which fails to give a
coherent mass

Grindability Index
It is important in connection with pulverizing.
Specially sized coal is submitted to a standardized grinding procedure.
The index is calculated from the percentage of the sample remained on a
74 micron sieve

Storage, Handling and Preparation of Coal

Uncertainty in the availability and transportation of fuel necessitates storage
and subsequent handling. Stocking of coal has its own disadvantages like buildup of inventory, space constraints, deterioration in quality and potential fire
hazards. Other minor losses associated with the storage of coal include
oxidation, wind and carpet loss. A 1% oxidation of coal has the same effect as
1% ash in coal, wind losses may account for nearly 0.5 1.0% of the total loss.
The main goal of good coal storage is to minimise carpet loss and the loss due to
spontaneous combustion. Formation of a soft carpet, comprising of coal dust
and soil causes carpet loss. On the other hand, gradual temperature builds up in
a coal heap, on account of oxidation may lead to spontaneous combustion of
coal in storage.
The measures that would help in reducing the carpet loses are as follows:
Preparing a hard ground for coal to be stacked upon.
Preparing standard storage bays out of concrete and brick
In process Industry, modes of coal handling range from manual to conveyor
systems. It would be advisable to minimise the handling of coal so that further
generation of fines and segregation effects are reduced.

Preparation of Coal
Preparation of coal prior to feeding into the
boiler is an important step for achieving good
combustion. Large and irregular lumps of coal
may cause the following problems:
Poor combustion conditions and inadequate
furnace temperature.
Higher excess air resulting in higher stack
loss.
Increase of unburnts in the ash.
Low thermal efficiency.

Sizing of Coal
Proper coal sizing is one of the key measures to ensure efficient combustion.
Proper coal sizing, with specific relevance to the type of firing system, helps
towards even burning, reduced ash losses and better combustion efficiency.
Coal is reduced in size by crushing and pulverizing. Pre-crushed coal can be
economical for smaller units, especially those which are stoker fired. In a coal
handling system, crushing is limited to a top size of 6 or 4mm. The devices most
commonly used for crushing are the rotary breaker, the roll crusher and the
hammer mill.
It is necessary to screen the coal before crushing, so that only oversized coal is
fed to the crusher. This helps to reduce power consumption in the crusher.
Recommended practices in coal crushing are:
Incorporation of a screen to separate fines and small particles to avoid
extra fine generation in crushing.
Incorporation of a magnetic separator to separate iron pieces in coal,
which may damage the crusher.

Conditioning of Coal
The fines in coal present problems in combustion on account of
segregation effects. Segregation of fines from larger coal pieces
can be reduced to a great extent by conditioning coal with water.
Water helps fine particles to stick to the bigger lumps due to
surface tension of the moisture, thus stopping fines from falling
through grate bars or being carried away by the furnace draft.
While tempering the coal, care should be taken to ensure that
moisture addition is uniform and preferably done in a moving or
falling stream of coal.
If the percentage of fines in the coal is very high, wetting of coal
can decrease the percentage of unburnt carbon and the excess air
level required to be supplied for combustion. Table 1.9 shows the
extent of wetting, depending on the percentage of fines in coal.

Blending of Coal
In case of coal lots having excessive fines, it is
advisable to blend the predominantly lumped coal
with lots containing excessive fines. Coal blending may
thus help to limit the extent of fines in coal being fired
to not more than 25%. Blending of different qualities
of coal may also help to supply a uniform coal feed to
the boiler.

calorific value= Q = 337C + 1442(H - O/8) + 93S

where
C is the mass percent of carbon,
H is the mass percent of hydrogen,
O is the mass percent of oxygen,
S is the mass percent of sulfur in the coal. With these constants, Q is given in
kilojoules per kilogram.