Chapter 12
CHAPTER NO.12 CONVENTIONAL SOURCES OF
ENERGY
Energy is harnessed from a variety of sources, The
major conventional sources of energy in-clude the fossil fuels and firewood.
These sources account for most of the total energy consumption
in the world. The fossil fuels (coal, oil, natural
gas) are also known as non-renewable sources of energy because of their limited
reserves in nature, It took millions of years in nature to form fossil fuels
from the marine organism and green plants. The excessive use of these sources
during the past century has resulted in widespread pollution of the
environment.
COAL ;
Coal is a solid formed from green plants trapped
under sediments in millions of years, The vatying degree of temperature and
pressure during decomposition resulted in formation of different
grades of coal. These grades differ in content of
carbon, moisture and volatile compounds present in them, Lignite is a moist and
soft grade of coal. It is brown or blackish brown in colour, It produces little
heat than other grades of coal. The most common type of coal is bituminous
coal. This brilliant
black coloured grade is harder than lignite,
contains sulphur and produces lot of heat on burning. The highest heat
producing grade of coal is anthracite. It is hard, brilliant black and burns
most cleanly causing relatively less pollution than other grades. All the three
grades of coal present as underground deposits are removed through process of
coal mining. Coal has proved as backbone of industrializa-tion. It replaced the
use of firewood. In addition to use as a major fuel in industry, coal is also
used in preparation of coke, coal gas, synthetic petroleum and many organic
compounds such as benzene,toluene, aniline, anthracine etc. Coal is the most
abundant fossil fuel and its major deposits are in the United States of
America, former Soviet Union and China, As per estimates made by Geological
Survey of India (GSI) during January 2001, the
proven coal reserves in India contain about 84.41 billion tonnes of coal. These
reserves may last for about 200 years in future. Most of the coal
reserves are located in Bihar, West Bengal, Andhra
Pradesh, Madhya Pradesh and Maharasthra, In India, coal alone accounts for half
of the total energy supply and about 60 percent of the coal is used for
electricity generation. The demand is rising year after year.
The coal mining process and subsequent use of coal
for different purposes cause substantial damage to the environment. During
mining operations, vegetation and top soil are removed, This activity destroys
natural habitats of wild animals. Burning of coal releases carbon dioxide,
sulphur oxides and nitrogen oxides info the atmosphere. The long term emission
of carbon dioxide since the industrial revolution, has initiated the problem of
global warming. More amount of carbon dioxide per unit of heat is produced by
burning of coal in comparison with other fossil fuels. The oxides of sulphur
and nitrogen combine with water vapours present in the atmosphere and produce
acid rain.
Smoke generated due to coal buming contains solid
particulate matter and results in pollution of the air, The workers engaged in
underground coal mining operations suffer from health injuries and res-piratory
disorders. The uninterrupted supply of coal to distantly located thermal power
plants is not an easy task.
OIL:
Crude oil or petroleum is a dark oily liquid made up
mostly of hydrocarbon compounds and small quantities of compounds containing
sulphur, nitrogen and oxygen. The word petroleum is de-
tived from the Greek words,petra meaning rock and
oleum meaning oil. It was
formed in nature when large number of marine
micro-scopic organisms died and
got trapped under sediments.
Under the effect of heat and pressure these dead
organ-iams got converted into crude oil over millions of years. The
presence of a petroleum de-posit is detected through
ex-ploration of impermeable rocks that form structural
traps around it, The wells are drilled at promising
sites and the petroleum is pumped out.It is then separated into use-ful products
such as gasoline
(petrol), diesel, kerosene,naphtha, asphalt etc,
This pro-cess of separating crude oil into different useful components is known
as refining of petroleum (Fig. 12.1). For this purpose, petroleum is subjected
to fractional distillation. This process in-volves heating of crude oil to
evaporate different components at their specific boiling points. In the
fractionating tower, these uprising vapours of different components condense at
different levels and are subsequently collected. Fractional distillation of
crude oil provides us useful products and by products.
Petroleum products such as diesel and gasoline are
used in transport sector. The liquefied pe-troleum gas (LPG) collected during
refining of petroleum is used as source of energy for cooking and heating. The
petrochemicals obtained from crude oil are used in production of fertilizers,
paints,plastics,pesticides, synthetic fibres and medicines.
Crude oil has emerged as a major source of energy
since 1940s. It is easy to transport and burns more cleanly than coal. In
India, about 40 percent of the petroleum products are used in
transportation and the rest is used in industry and
some other sectors. The domestic crude oil production of 33million metric tones
(2000-2001) is sufficient to meet about 35 percent of the annual demand.
Contrary to this, the demand for petroleum products is rising very rapidly and
our dependence on import is vastly increasing. The Indian crude oil deposits
are 0.4 percent of the world's total proven reserves. These are mainly located
in the states of Assam and Gujarat. The Organization of Petroleum Exporting
Countries (OPEC) holds 77 percent of the world's total oil reserves.
As in case of coal, burning of oi] also produces
carbon dioxide and partly contributes to the problem of global warming. The
nitrogen oxides released from buming of gasoline (petrol) in auto-mobiles lead
to acid precipitation in the atmosphere. The oil spills occured during
transportation of
crude oil also result in severe damage to aquatic
animals living in oceans, The out breaking of fire at oil refineries and oil
deposits also causes air pollution.
NATURAL GAS :
It is a mixture of a few different hydrocarbons.
These include especially the methane and smaller amounts of propane and butane.
Natural gas was formed in nature in the same way as
crude oil ot petroleum, from marine microscopic
animals trapped under the sediments over mil-lions of years. Most of the
natural gas lies above deposits of petroleum. Sometimes, it also occurs
without petroleum, Butane and propane are removed
from the natural gas, These are then stored in pressurized tanks or cylinders
in the form of liquefied petroleum gas (LPG) that is used for
cooking and heating. The remaining gas (methane) is
then cleaned of impurities and pumped into pipelines for further distribution,
It can be converted into liquefied natural gas (LNG) at very low
temperature. Specially designed refrigerated tanker
ships are used for transportation of liquefied petroleum gas.
Natural gas is used to generate electricity in power
plants. It is used as a fuel in industries associated with manufacture of
cement, ceramics, glass, bricks and food processing. Petrochemicals are also
obtained from natural gas. These are used in production of plastics, medicines,
detergents,fertilizers etc. The compressed natural gas (CNG) is used as a fuel
in automobiles. In developed
countries, it is also used to heat residential and
commercial buildings. In India, the proven reserves of
natural gas are about 749.65 billion cubic metre
(BCM). The major reserves are in Assam, Gujarat and Bombay High. This energy
source accounts for about 10 percent of the power generation.
Efforts are being made to explore more gas reserves
and setting up of supply pipelines.
Natural gas is the cleanest and hottest fossil fuel.
It can be easily transported by pipelines.Liquefied natural gas (LNG) is highly
volatile and inflammable. Accidents, when occur during trans-portation of
natural gas over long distances by pipelines or specially designed tanker ships
cause
damage both to human life and environment.
FIREWORD:
The fuelwood or firewood has been a major source of
energy since early civilization. Till the middle of nineteenth century, it
remained the most important source of energy. About half of the world
population still depends upon firewood as primary source of energy for cooking
and heating.Firewood is obtained from forests and is considered as a
non-commercial source of energy. On burning, the chemical energy of wood
trapped by photosynthesis is converted to heat energy. Fire-wood has several
disadvantages. It contains a lower energy content and high moisture content per
unit of weight. When bumtt, it releases large amount of smoke and leads to
indoor and outdoor air
pollution, Oxides of sulphur and nitrogen also get
added into the atmosphere. In India, the people
living in rural areas obtain 80 percent of their
total energy from firewood, animal waste and crop residues.
On a sustainable basis, our forests can provide only
28 million tones of firewood every year.But the demand of firewood is much
higher than this available quantity. This demand is further in-creasing due to
rising population. As a result, there is a pressure on our forests. Fire-wood
is a
renewable source only if the forests are not
harvested faster than they grow back.
EXERCISE
(A) Very short answer type questions (1
mark each) :
1, Name major conventional sources of energy.
2, Which is the highest heat producing grade of
coal?
3. Name the most abundant fossil fuel found in
nature,
4. Where are the major coal reserves located in
India?
5. What is the composition of petroleum?
6. What do you understand by refining of petroleum?
7. Name two important petroleum products which are
used in transport sector.
8. Name the major hydrocarbon present in natural
gas,
9, Which one is the cleanest and hottest fossil
fuel?
10. What is the source of firewood?
(B) Short answer type questions (2
marks each) :
1, Why are the fossil fuels known as non-renewable
sources of enegy?
2. How was the coal formed in nature?
3. Write two important uses of coal.
4. How was the petroleum produced in nature?
5, What are the uses of LPG and petrochemicals?
6. How is LPG obtained from natural gas?
7. Differentiate between LNG and CNG.
8. What are the risks associated with use of natural
gas?
9. Why is the demand of firewood increasing every
year?
(C) Short answer type questions (4
marks each):
1, Write a short note on different grades of coal.
2, What are the adverse effects of coal mining?
3. How does coal buming affect the environment?
4. Explain the process of fractional distillation.
5. What are the consequence of petroleum use?
6. What are the important uses of natural gas?
7. Give some disadvantages of firewood.
Long answer type questions: (5 marks
each):
1. White about formation, extraction, grades and
uses of coal.
2. Discuss fromation, extraction, refining and uses
of petroleum.
3. Describe the limitations and environmental
consequences associated with fossil fuels.
