11.3 fuels effects of burning

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Chemistry(14 - 16)

Chemistry(14 - 16)

Fuels(Effects of Burning)

Fuels(Effects of Burning)

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 OilCombustion 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.

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

Motorcycles burn petrol...

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

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

Trains burn diesel...

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

Large ships burn heavy fuel oil.

The Burning of FuelsThe 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...

CH4(g) + 2O2(g) CO2(g) + 2H2O(g) + energy

+ oxygen carbon dioxide + water + energymethane

(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.

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...

For safety reasons, a sulfurous additive is combined with natural

gas to give it its characteristic smell of bad eggs.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 is mostly methane, so when it is combusted in air, we consider it to effectively be the combustion of methane.

Natural Gas or Methane?Natural Gas or Methane?

In excess oxygen, the equation for combustion of methane is:

CH4 + 2O2 CO2 + 2H2O

methane oxygen carbon dioxide water

The Complete Combustion of Methane in AirThe Complete Combustion of Methane in Air


In excess oxygen, the equation for combustion of methane is:

CH4 + 2O2 CO2 + 2H2O


CH4 + 2O2 CO2 + 2H2O


The photograph shows a bunsen flame where complete combustion is taking place.


The blue flame is characteristic of complete combustion.

The air hole is fully open and so thereis ample air (oxygen) supply.

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:

2CH4 + 3O2 2CO + 4H2O

methane oxygen carbon monoxide water

The Incomplete Combustion of Methane in AirThe Incomplete Combustion of Methane in Air

CH4 + O2 C + 2H2O

methane oxygen carbon water

Incomplete combustion may have these additional reactions taking place at the same time:

methane + oxygen carbon + carbon + carbon + waterdioxide monoxide

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

2CH4 + 3O2 2CO + 4H2O

methane oxygen carbon monoxide water

CH4 + O2 C + 2H2O

methane oxygen carbon water

The Incomplete Combustion of Methane in AirThe 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 characteristicyellow colour.

As the electrons of the carbon atoms lose energy they emit light.

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 + O2 SO2

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 The Combustion of Sulfur within Fuels

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 Environmental Impact

Carbon Dioxide

Sulfur Dioxide

Carbon Particles

Acid RainAcid 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.

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.

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 RainAcid Rain

Acid rain also increases the rate at which carbonate rocks and ancient buildings made of limestone, are being weathered.

Acid RainAcid Rain

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

The following Pie Chart shows the various UK contributors to atmospheric SO2.

What can be done to reduce these emissions?

Reducing Acid Rain - SO2 EmissionsReducing Acid Rain - SO2 Emissions

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 - SO2 EmissionsReducing Acid Rain - SO2 Emissions

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 ScrubberReducing Acid Rain - Using a Scrubber

Reducing Acid Rain - Using a ScrubberReducing 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.

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 ConvertersReducing 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.

Catalytic ConverterCatalytic Converter

Move the cursor over the red circles to find out more...

SO2 Source% SO2

Produced in UK

Power Stations 65

Domestic & Commercial 6

Oil Refineries, Iron & Steel Production 12

Other Industry 10

Transport 3

Other 4

Sources of SO2 in the UK (1999)Sources of SO2 in the UK (1999)

Discuss the data in the table...

The Greenhouse EffectThe Greenhouse EffectMove the cursor over the diagram to find out more...

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 CO2 and other air pollutants increase, they trap even moreof 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 theshort wave, infra redradiation emittedby the Sun penetrates the Earth’s outer atmosphereand warms the Earth.

CO2

CO2

CO2

CO2

CO2

CO2

CO2

The Greenhouse EffectThe Greenhouse Effect

Global DimmingGlobal Dimming

Global dimming is caused by the burning of organic material suchas fossil fuels and wood. Many sources contribute to globaldimming, e.g. in power stations, car engines, burning forests and even wood for cooking.

Global dimming is caused by the burning of organic material suchas fossil fuels and wood. Many sources contribute to globaldimming, 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.

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.

Global DimmingGlobal 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.

Global Dimming - SummaryGlobal Dimming - SummaryMove your cursor over the diagram to find out more...

Global Warming v Global DimmingGlobal 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 fora few days. During this time, because there was less pollution and cloud formation, the temperature of the Earth rose significantly.

Reducing the Environmental

Impact

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 CO2 per passenger than the all the rest of the annual CO2 production allocated per person.

As fossil fuel supplies run out, newer types of fuels are being developed, such as biodiesel, ethanol and hydrogen.

Alternative Fuels - EthanolAlternative Fuels - Ethanol

A supply of sugar beet, used for making ethanol.

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 - BiodieselAlternative Fuels - Biodiesel

Alternative Fuels - HydrogenAlternative Fuels - HydrogenHydrogen 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...

Alternative Fuels - HydrogenAlternative Fuels - HydrogenHydrogen 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 CO2. The hydrogen is also difficult to store safely.

Move your cursor over the diagram to find out more...

Alternative Fuels: HydrogenAlternative Fuels: Hydrogen

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

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

11.3 fuels effects of burning

Education

Transcript of 11.3 fuels effects of burning