11.3 fuels effects of burning

Yr 11 Chem Energy

1. © SSER Ltd.
Chemistry
(14 - 16)
Fuels
(Effects of Burning)

2. Oil refineries produce large volumes of fuel to power modern
forms of transport, and for many other uses. The different fuels
are produced from the fractional distillation of crude oil.
Petrol ignites below 0ºC
Diesel ignites above 50ºC
Fuel oil ignites above 100ºC
Ethanol ignites above 13ºC
Combustion of Fuels Produced From Crude Oil
These combustion properties affect how each fuel is used...
Different fuels have different sized molecules. The size of the
molecules affect how easily the fuel ignites and burns, e.g.

3. Jet engines of modern aeroplanes burn light jet fuel...

4. Motorcycles burn petrol...

5. Cars burn petrol or diesel. Some are even being modified
to run on biofuels such as ethanol or biodiesel...

6. Public transport would grind to a halt without diesel...

7. Trains burn diesel...

8. Power stations like this one at Immingham, next to a major oil
refinery, now burn diesel fuel to generate electricity for the
National Grid.

9. Large ships burn heavy fuel oil.

10. The Burning of Fuels
The burning of fuels in air is called combustion.
As heat energy is given out, this is an exothermic reaction.
Example: methane is a fuel used in many homes...
CH
4(g)
+ 2O
2(g)
Þ CO
2(g)
+ 2H
2
O
(g)
+ energy
+ oxygen Þ carbon dioxide + water + energy
methane
(fuel)
All fuels will burn in air (combustion) to produce carbon
dioxide and water. Other chemicals products may be made, e.g.
carbon monoxide, sulfur dioxide and carbon.

11. The Complete Combustion of Methane in Air
90% Methane
5% Ethane
3% Nitrogen
1.0% Propane
0.5% Carbon dioxide
0.5% Butane
Natural gas consists of...

12. For safety reasons, a sulfurous additive is combined with natural
gas to give it its characteristic smell of bad eggs.
Natural gas is mostly methane, so when it is combusted in air, we
consider it to effectively be the combustion of methane.
Natural Gas or Methane?

13. In excess oxygen, the equation for combustion of methane is:
CH
4
+
2O
2
Þ

CO
2
+
2H
2
O
methane oxygencarbon dioxide water
The Complete Combustion of Methane in Air

14. The Complete Combustion of Methane in Air
In excess oxygen, the equation for combustion of methane is:
CH
4
+
2O
2
Þ

CO
2
+
2H
2
O
methane oxygencarbon dioxide water

15. CH
4
+
2O
2
Þ

CO
2
+
2H
2
O
methane oxygencarbon dioxide water
The photograph shows a bunsen
flame where complete combustion is
taking place.
The Complete Combustion of Methane in Air
The blue flame is characteristic of
complete combustion.
The air hole is fully open and so there
is ample air (oxygen) supply.

16. Where oxygen levels are limited, incomplete combustion occurs.
This is a more complex process made up of a number of possible
reactions. This word equation shows the possible products:
2CH
4
+ 3O
2
Þ

2CO + 4H
2
O
methane oxygen carbon monoxidewater
The Incomplete Combustion of Methane in Air
CH
4
+ O
2
Þ C + 2H
2
O
methaneoxygen carbon water
Incomplete combustion may have these additional reactions taking
place at the same time:
methane +
oxygen
Þ

carbon +
carbon + carbon + water
dioxidemonoxide

17. Many people die in their homes or whilst on holiday, as a result of
carbon monoxide poisoning, due to faulty gas fires and central
heating boilers - carbon monoxide is a colourless, odourless gas!
Carbon Monoxide Poisoning
2CH
4
+ 3O
2
Þ

2CO + 4H
2
O
methane oxygen carbon monoxidewater

18. CH
4
+ O
2
Þ C + 2H
2
O
methaneoxygen carbon water
The Incomplete Combustion of Methane in Air
The photograph shows a bunsen
flame where incomplete combustion is
taking place. The air hole is closed
and so the air (oxygen) supply is
restricted.
It is the carbon atoms that give the
safety flame its characteristic
yellow colour.
As the electrons of the carbon atoms
lose energy they emit light.

19. Although most fuels are mainly hydrocarbons, they also contain
low levels of sulfur. This means that during combustion, in excess
levels of oxygen, the following reaction also takes place:
S

+
O
2
Þ

SO
2
sulfur dioxideoxygensulfur
The sulfur dioxide, carbon dioxide and carbon particles produced
by combustion are all linked to environmental problems...
The Combustion of Sulfur within Fuels

20. Carbon dioxide is linked to the greenhouse effect. Increased levels
of carbon dioxide are trapping the Sun’s energy, causing the
climate to warm up.
Sulfur dioxide is linked to acid rain. Increased levels of sulfur
dioxide are turning rain water acidic, causing fish and trees to die.
Carbon particles are linked to global dimming. Increased levels of
carbon particles are causing more sunlight to be reflected, which
reduces the total sunlight reaching the Earth.
Environmental Impact
Carbon Dioxide
Sulfur Dioxide
Carbon Particles

21. Acid Rain
Acid rain is caused by burning fossil fuels, which contain small
amounts of sulfur and nitrogen. During the burning, sulfur and
nitrogen are converted to sulfur dioxide and nitrogen dioxide.

22. When it rains, these acids fall to the Earth as acid rain.
This process decreases the pH of soil and the water in lakes and
rivers, which kills trees and fish.
Acid Rain
Acid rain also increases the rate at which carbonate rocks and
ancient buildings made of limestone, are being weathered.

23. Acid Rain
Use the interactive diagram to find out more about acid rain...

24. The following Pie Chart shows the various UK contributors to
atmospheric SO
2
.
What can be done to reduce these emissions?
Reducing Acid Rain - SO
2
Emissions

25. To reduce the levels of sulfur dioxide produced by burning fuels,
a number of strategies have been adopted:
Many refineries remove
sulfur during the refining
process allowing fuel
stations to offer low sulfur
fuels to their customers.
Power stations are fitted with a scrubber, a device which
removes sulfur dioxide...
Reducing Acid Rain - SO
2
Emissions

26. A scrubber (fluid gas desulfuriser or FGD unit) is a device fitted to
fossil fuel power stations, which removes the sulfur dioxide from
waste gases. The FGD sprays the flue gases with a limestone/water
mixture producing gypsum, which is used in the building industry.
Reducing Acid Rain - Using a Scrubber

27. Reducing Acid Rain - Using a Scrubber
A scrubber (fluid gas desulfuriser or FGD unit) is a device fitted to
fossil fuel power stations, which removes the sulfur dioxide from
waste gases. The FGD sprays the flue gases with a limestone/water
mixture producing gypsum, which is used in the building industry.

28. Catalytic converters are now fitted as standard to all car exhausts.
Normal car exhaust gases contain unburnt petrol, oxides of
nitrogen (which contribute to acid rain) and carbon monoxide.
Reducing Acid Rain - Catalytic Converters
Catalytic converters, containing the transition metal platinum,
cause a reaction between these polluting gases to produce harmless
gases, such as nitrogen, oxygen, carbon dioxide and water vapour.

29. Catalytic Converter
Move the cursor over the red circles to find out more...

30. % SO
2

Produced in UK
SO
2
Source
65Power Stations
6Domestic & Commercial
4Other
3Transport
10Other Industry
12Oil Refineries, Iron & Steel Production
Sources of SO
2
in the UK (1999)
Discuss the data in the table...

31. The Greenhouse Effect
Move the cursor over the diagram to find out more...

32. Greenhouse gases
within the Earth’s
atmosphere absorb
some of this
outgoing radiation
and reflect it back
to the Earth’s
surface.
As levels of CO
2
and other air pollutants increase, they trap even more
of the outgoing heat radiation causing even more global warming.
Some of this
radiation is
re-emitted from
the earth as long
wave radiation.
About 80% of the
short wave, infra red
radiation emitted
by the Sun penetrates the
Earth’s outer atmosphere
and warms the Earth.
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
The Greenhouse Effect

33. Global Dimming
Global dimming is caused by the burning of organic material such
as fossil fuels and wood. Many sources contribute to global
dimming, e.g. in power stations, car engines, burning forests and
even wood for cooking.
The burning releases particles of soot and ash which reflect
sunlight back into space - thus preventing the sunlight from
reaching the Earth’s surface. It is this effect whereby less light
penetrates the atmosphere which is known as global dimming.

34. Global Dimming
The soot and ash particles also trigger the formation of water
droplets in clouds and cause the production of many more droplets,
which increases a cloud’s reflective properties. This further
increases the amount of solar radiation reflected into space.

35. Global Dimming - Summary
Move your cursor over the diagram to find out more...

36. Global Warming v Global Dimming
Scientists now believe that global dimming has been working
against global warming. The dimming caused by pollution has
reduced the effect of global warming, which would have been
much worse otherwise.
A worrying consequence of cleaning up pollution, is that the full
effect of global warming will be felt, and the planet will warm up
at an even faster rate.
The effect of global dimming was clearly shown, immediately after
the 9/11 terrorist attacks, after which all flights were cancelled for
a few days. During this time, because there was less pollution and
cloud formation, the temperature of the Earth rose significantly.

37. Reducing the
Environmental
Impact
One suggestion is not to fly
so often - perhaps we will
only be allowed to go
abroad once every few years
or a new tax will be put on
non essential flights.
One flight abroad on a
summer holiday produces
more CO
2
per passenger
than the all the rest of the
annual CO
2
production
allocated per person.

38. As fossil fuel supplies run out, newer types of fuels are being
developed, such as biodiesel, ethanol and hydrogen.
Alternative Fuels - Ethanol
A supply of sugar beet, used for making ethanol.

39. This reaction is called
transesterification.
Biodiesel can be made from
rapeseed, soybean, palm oil or
even recovered cooking oils.
Biodiesel is used as a fuel in diesel engines. However, if this biofuel
is dissolved in petrol or ethanol, it can be used in petrol engines.
Straight vegetable oil (SVO) can be used in place of ordinary
diesel. Vegetable oil can be improved as a fuel by reacting it with
methanol, using sodium hydroxide or potassium hydroxide as a
catalyst. This produces biodiesel.
Alternative Fuels - Biodiesel

40. Alternative Fuels - Hydrogen
Hydrogen can be produced from either water or natural gas. It is
then combined with oxygen inside a fuel cell to produce electricity,
which can power a car.
Move your cursor over the diagram to find out more...

41. Alternative Fuels - Hydrogen
Hydrogen can be produced from either water or natural gas. It is
then combined with oxygen inside a fuel cell to produce electricity,
which can power a car.
However, the production of electricity (non-renewable energy
sources) used to produce the hydrogen (from water) releases large
volumes of CO
2
. The hydrogen is also difficult to store safely.
Move your cursor over the diagram to find out more...

42. Alternative Fuels: Hydrogen
This concept car with a hydrogen engine may be the way forward
for land transport. It certainly is modern technology...

43. Energy Use
Environmentalists argue for energy conservation, to reduce the
effects of global warming.
Move your cursor over each student to see their points of view...

44. End of Show
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