Presentation on theme: "1 Chapter 27Environmental Problems Associated with Use of Fuels 27.1Environmental problems associated with fossil fuels 27.2Combustion products from fossil."— Presentation transcript:
1 Chapter 27Environmental Problems Associated with Use of Fuels 27.1Environmental problems associated with fossil fuels 27.2Combustion products from fossil fuels 27.3Air pollution 27.4Acid rain 27.5Controlling acid rain 27.6Ways to cut down pollutants from the burning of fuels 27.7Air pollution problems in Hong Kong CONTENTS OF CHAPTER The global greenhouse effect 27.9Pollution problems associated with oil spillage 27.10Energy crisis and alternative energy sources
2 27.1ENVIRONMENTAL PROBLEMS ASSOCIATED WITH FOSSIL FUELS Fossil fuels are convenient to use and relatively cheap. However, they create environmental problems in the following respects: (1)Extraction and processing (2)Transportation (3)Burning 27.1 ENVIRONMENTAL PROBLEMS ASSOCIATED WITH FOSSIL FUELS
COMBUSTION PRODUCTS FROM FOSSIL FUELS PRODUCTS FROM COMPLETE COMBUSTION In good supply of air, fossil fuels usually burn to form carbon dioxide and water as the main products. PRODUCTS FROM INCOMPLETE COMBUSTION When there is not enough air, carbon in a fuel burns to form carbon monoxide (instead of carbon dioxide). If the air supply is really poor, unburnt carbon particles would come out as soot and black smoke.
4 PRODUCTS FROM IMPURITIES IN FUELS Some fuels, particularly coal, contain a little sulphur. When they burn, sulphur dioxide is produced as one of the products. COMBUSTION PRODUCTS FROM PETROL IN AN INTERNAL COMBUSTION ENGINE Petrol is an oil fraction containing mainly C 5 to C 10 hydrocarbons, with boiling point range 40 – 170 o C. Most motor vehicles are powered by internal combustion engines which burn petrol. In a car engine, petrol is burnt in cylinders COMBUSTION PRODUCTS FROM FOSSIL FUELS
5 Figure 27.2 A car engine COMBUSTION PRODUCTS FROM FOSSIL FUELS
6 A typical reaction which occurs would be: 2C 8 H 18 (g) + 25O 2 (g) 16CO 2 (g) + 18H 2 O(g) Due to incomplete combustion, carbon monoxide and unburnt carbon will also be formed. Besides, some petrol may be unburnt. Thus there are vapours of hydrocarbons. The combined action of high temperatures and electric sparks causes a little atmospheric nitrogen and oxygen (inside cylinders) to combine: N 2 (g) + O 2 (g) 2NO(g) 2NO(g) + O 2 (g) 2NO 2 (g) Combustion products from leaded petrol also contain lead compounds COMBUSTION PRODUCTS FROM FOSSIL FUELS
7 Table 27.1 Typical composition of car exhaust gases COMBUSTION PRODUCTS FROM FOSSIL FUELS
AIR POLLUTION CAUSES OF AIR POLLUTION Air pollutants are from two sources: natural processes and human activities. Figure 27.6 Volcanoes are natural sources of air pollutants.
9 Figure 27.7 Sources of pollutants produced by humans AIR POLLUTION Motor vehicles Factories Power stations Incinerators
10 MAIN AIR POLLUTANTS The greatest source of air pollutants is motor vehicles — from burning petrol or diesel. Electric power stations and factories also produce a lot of pollutants when they burn coal or oil fractions to produce energy. Incinerators pollute the air in burning waste. AIR POLLUTION is the presence in air of undesirable substances at so high a concentration as to be harmful to health or to property AIR POLLUTION
12 A27.1 Carbon monoxide, formed by the incomplete combustion of fuel, will build up to dangerous levels in an enclosed space. It may cause death AIR POLLUTION
13 Figure 27.8 New York City, before and during a photochemical smog. (a)(b) 27.3 AIR POLLUTION
14 Figure 27.9 Black smoke from (a)factories (b) motor vehicles. (a)(b) 27.3 AIR POLLUTION
15 A27.2 A27.3 No, because many pollutants (e.g. sulphur dioxide, carbon monoxide, hydrocarbons) are colourless gases. (a)Carbon monoxide, nitrogen oxides (nitrogen monoxide, nitrogen dioxide), hydrocarbons, and suspended particulates (e.g. lead, lead(II) compounds, smoke, soot). (b)Sulphur dioxide, nitrogen oxides (or carbon monoxide) AIR POLLUTION
ACID RAIN FORMATION OF ACID RAIN Rainwater with pH values lower than 5.7 is called acid rain. Two air pollutants are responsible for acid rain — sulphur dioxide and nitrogen dioxide.
17 Figure Acid rain usually has a pH between 2.5 and 5. Just imagine that rain as acidic as vinegar (with pH = 3) pouring from the sky! 27.4 ACID RAIN
18 SO 2 (g) + H 2 O(l) H 2 SO 3 (aq) sulphurous acid 2H 2 SO 3 (aq) + O 2 (g) 2H 2 SO 4 (aq) 2NO 2 (g) + H 2 O(l) HNO 3 (aq) + HNO 2 (aq) 27.4 ACID RAIN
19 Figure Formation of acid rain ACID RAIN
20 A27.4 A27.5 Both statements are correct, but the second one does not explain the first one. Actually, the low pH of acid rain is caused by the dissolved sulphur dioxide and nitrogen dioxide. Probably at that time, the many factories in the Kwun Tong industrial district used fuels of high sulphur content. The large amount of sulphur dioxide resulted in acid rain ACID RAIN
ACID RAIN To test sulphur dioxide and nitrogen dioxide for acidity.
22 WHAT HARM DOES ACID RAIN CAUSE? Acid rain causes harm to vegetation, water life and building materials. Vegetation Acid rain makes soils acidic. Many plants cannot grow well in acidic soils. As a result, acid rain damages crops and destroys forests ACID RAIN
23 Figure These trees are believed to have been killed by acid rain ACID RAIN
24 Water life Water in the majority of lakes and some rivers in the world has become acidic due to acid rain. Fish and water plants cannot survive in water which is too acidic (with a pH lower than 5). Building materials Acid rain has bad effects on common building materials which contain calcium carbonate. Calcium carbonate reacts readily with acids: CaCO 3 (s) + 2H + (aq) Ca 2+ (aq) + CO 2 (g) + H 2 O(l) 27.4 ACID RAIN
25 Figure Acid rain has corroded this statue ACID RAIN
CONTROLLING ACID RAIN The following are some possible ways: Cut down pollutants from the burning of fuels Burn less fossil fuels. This can be achieved by using energy more efficiently and using alternative energy sources Neutralize the acids in soil and water (by calcium hydroxide or calcium carbonate)
WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS 27.6WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS CUTTING DOWN POLLUTANTS FROM MOTOR VEHICLES Using unleaded petrol By using unleaded petrol in motor vehicles, we can greatly reduce lead emission into the air.
28 Figure Using unleaded petrol for a better environment WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
29 Fitting catalytic converters to motor vehicles Motor vehicles fitted with catalytic converters would produce ‘cleaner’ exhaust gases. platinum as 2CO(g) + 2NO(g) 2CO 2 (g) + N 2 (g) catalyst poisonous gasesharmless gases 27.6 WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
30 Figure (a) A catalytic converter. (b)A catalytic converter fitted to the car exhaust system WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
31 catalyst 2CO(g) + O 2 (g) 2CO 2 (g) C x H y (l) + (x + ) O 2 (g) xCO 2 (g) + H 2 O(l) Using LPG instead of diesel LPG is a much cleaner fuel than diesel. Using alcohol instead of petrol Alcohol is a cleaner fuel than petrol. In some countries (e.g. Brazil), cars run on alcohol or gasohol (a mixture of petrol and alcohol). y4y4 y2y WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
32 CUTTING DOWN POLLUTANTS FROM INDUSTRY Reducing sulphur dioxide emission We can reduce sulphur dioxide emission by burning fuels of low sulphur content. In tanks called scrubbers, the waste gases are sprayed with jets of limewater before they come out of the chimneys. The limewater dissolves soluble acidic gases (mainly sulphur dioxide). Removing particulates from industrial emission We can remove particulates from waste gases by mechanical filtering. Alternatively, we can use electrostatic precipitators WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
33 Increasing the height of chimney stacks Increasing the height of chimney stacks can spread waste gases over a larger area WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
34 Figure Taller chimney stacks in incinerators can spread waste gases over a larger area WAYS TO CUT DOWN POLLUTANTS FROM THE BURNING OF FUELS
THE GLOBAL GREENHOUSE EFFECT GREENHOUSE AND GREENHOUSE EFFECT 27.8 THE GLOBAL GREENHOUSE EFFECT
36 Figure A local greenhouse and the greenhouse effect THE GLOBAL GREENHOUSE EFFECT
37 Figure The greenhouse effect of the Earth THE GLOBAL GREENHOUSE EFFECT
38 The GLOBAL GREENHOUSE EFFECT (or simply GREENHOUSE EFFECT) refers to the trapping of infrared radiation by carbon dioxide and other gases in the atmosphere, keeping the Earth warm. The greenhouse effect is essential for life on Earth. Gases which are responsible for the greenhouse effect are called greenhouse gases. Carbon dioxide is the main greenhouse gas THE GLOBAL GREENHOUSE EFFECT
39 A27.6 A27.7 Burning fossil fuels produces carbon dioxide. More fossil fuels are burnt in winter to keep warm. Less fossil fuels are burnt in summer. Higher THE GLOBAL GREENHOUSE EFFECT
40 GLOBAL WARMING DUE TO ENHANCED GREENHOUSE EFFECT People burn a lot of fossil fuels, leading to a rapid increase of carbon dioxide concentration. This results in enhanced greenhouse effect, causing a rise in the Earth’s surface temperature (global warming) THE GLOBAL GREENHOUSE EFFECT
41 Figure The concentration of carbon dioxide in the atmosphere keeps on increasing THE GLOBAL GREENHOUSE EFFECT
42 Melting of ice caps at the North Pole and South Pole As a result, average sea levels would rise, causing disastrous flooding in low-lying coastal areas THE GLOBAL GREENHOUSE EFFECT
43 Figure An iceberg near the Pole. Many Polar ice caps will melt if the global temperature continues to rise! 27.8 THE GLOBAL GREENHOUSE EFFECT
44 Figure Sea defences at Holland. If the sea levels rise due to enhanced greenhouse effect, many parts of the world will need expensive sea defences THE GLOBAL GREENHOUSE EFFECT
45 Climate changes As the Earth heats up, there would be climate changes in different parts of the world. These changes would damage agriculture and reduce the world’s food supply. Wildlife in danger Flooding in coastal areas and climate changes would surely put wildlife in danger. FACING THE GLOBAL WARMING PROBLEM We can control carbon dioxide emissions by Reducing use of fossil fuels Stopping deforestation 27.8 THE GLOBAL GREENHOUSE EFFECT
46 Figure Rainforests help to remove carbon dioxide from air. At the same time, they add oxygen to air THE GLOBAL GREENHOUSE EFFECT
THE GLOBAL GREENHOUSE EFFECT Figure Clearing a forest would result in fewer trees to consume carbon dioxide.
48 Figure Forest fires destroy forests, at the same time adding carbon dioxide to the atmosphere. Preventing and putting out forest fires 27.8 THE GLOBAL GREENHOUSE EFFECT
49 Planting more trees 27.8 THE GLOBAL GREENHOUSE EFFECT
POLLUTION PROBLEMS ASSOCIATED WITH OIL SPILLAGE Major oil spills have occurred from accidents with off-shore oil wells and oil tankers. Besides, sea water is used to wash oil tanks in tankers, and a lot of oil escapes into the sea. Spilt oil threatens human safety and wildlife.
51 Figure Leakage of oil from a wrecked oil tanker POLLUTION PROBLEMS ASSOCIATED WITH OIL SPILLAGE
POLLUTION PROBLEMS ASSOCIATED WITH OIL SPILLAGE Figure A dying sea bird, its feathers being covered with oil.
ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES ENERGY CRISIS At present, more than 90% of the world’s energy needs is supplied by fossil fuels.
54 Figure Worldwide sources of energy. Fossil fuels (coal, petroleum, natural gas) account for most of the energy used ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
55 Fossil fuels are being used up quickly. Besides, they are not renewable. Figure How long fossil fuels will last ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES Figure A poster on conserving energy.
56 Activity 4 At present, fossil fuels supply more than 90% of the world’s energy needs. Advantages of using fossil fuel as energy sources: High calorific value Easily available Low price Easy to transport by pipeline, tankers, rail or motor vehicles Convenient to use Safe if properly used ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
57 Disadvantages of using fossil fuels as energy sources: Limited resources Not renewable Cause pollution problems Cause global warming Can be reserved for conversion into useful chemicals ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
58 NON-RENEWABLE AND RENEWABLE ENERGY SOURCES Fossil fuels are examples of non-renewable energy sources. On the other hand, solar power, hydroelectric power, tidal power, wind power, geothermal power and power from biomass are never used up. These are renewable energy sources ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
59 ALTERNATIVE ENERGY SOURCES Nuclear power Figure The Daya Nuclear Power Station ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
60 A27.8 (a)No. (b)Nuclear power is very clean, since it produces no air pollutants such as sulphur dioxide, carbon monoxide and nitrogen oxides. (A nuclear power station produces only one lorry load of radioactive waste each year. It can be sealed into tanks and buried deeply under the ground.) ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
61 Figure Solar heating panels on the roof of a house. Solar energy is used to heat up water in this house ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES Figure A calculator powered by solar cells. Solar power
62 Hydroelectric power Figure A view of the Qintong Gorge Hydropower Station ( 青銅峽水電廠 ) in China ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
63 A27.9 (a)It is a cheap, clean and renewable source of energy. (b)Many countries have neither sufficient rainfall nor high grounds to make hydroelectricity possible ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
64 Figure A tidal barrage in France. Electricity can be generated from the rise and fall of tides ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES Tidal power
65 Figure The high water flows though turbines which generate electricity ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES tidal barrage low water high water turbines
66 Figure Windmills to generate electricity. Wind power ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
67 Geothermal power Figure Geothermal power ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES Figure Extracting heat from underground.
68 Figure Biomass energy — a digester producing methane. Power from biomass ENERGY CRISIS AND ALTERNATIVE ENERGY SOURCES
70 SUMMARY 1.Incomplete combustion of fossil fuels may produce carbon monoxide, soot and smoke, apart from carbon dioxide and water. 2.Fossil fuels usually contain sulphur. They burn to produce sulphur dioxide as one of the products. SUMMARY
71 SUMMARY 4.Acid rain is rainwater with pH lower than 5.7. Two pollutants sulphur dioxide and nitrogen dioxide are responsible for acid rain. 3.Air pollutants from motor vehicles and industries:
72 SUMMARY 5.Acid rain would harm vegetation, water life and damage building materials. 6.The global greenhouse effect refers to the trapping of infrared radiation by carbon dioxide and other gases in the atmosphere, keeping the Earth warm. The greenhouse effect is essential for life on Earth. 7.Global warming due to enhanced greenhouse effect is mainly due to the excessive production of carbon dioxide from burning of fossil fuels. 8.Spillage of crude oil causes serious pollution problems to the water and coasts.
73 SUMMARY 9.At present, fossil fuels supply more than 90% of the world’s energy needs. Advantages of using fossil fuel as energy sources: High calorific value Easily available Low price Easy to transport by pipeline, tankers, rail or motor vehicles Convenient to use Safe if properly used
74 SUMMARY Disadvantages of using fossil fuels as energy sources: Limited resources Not renewable Cause pollution problems Cause global warming Can be reserved for conversion into useful chemicals 10.Fossil fuels are running out rapidly. It is important to save energy and look for alternative energy sources.