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Option F Fuels and Energy

By Tony Coleman,2014-11-26 17:06
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Option F Fuels and Energy

Option F : Fuels and Energy - Carolina Biasoli

The developments of human society has been directly related to the ability to use and manipulate

    fuels for energy production. This option considers the chemical principles and environmental

    issues associated with the use of fossil fuels, and nuclear and solar energy.

F.1 Energy Sources (1 h)

    F.1.1 State desirable characteristics of energy sources.

    ; Easily accessible

    ; Release energy at a reasonable rate

    ; Cheap

    ; Plentiful

    ; Not detrimental to environment

    ; Not detrimental to health

    F.1.2 Outline current and potential energy sources.

    ; Fossil fuels:

    ; Coal, oil, natural gas

    ; Non-renewable

    ; Contain carbon and hydrogen atoms

    ; Energy released when oxidized to form carbon dioxide and water

    ; Nuclear energy:

    ; Nuclear fission:

    o Large atomic nuclei split into smaller nuclei

    o Matter is converted into energy

    o Energy harnessed in nuclear power stations and converted into electricity

    o Large amounts of energy

    o Hard to control reactions

    o Problems associated with radioactive materials

    ; Nuclear fusion:

    o Potentially even more powerful

    o Combination of smaller nuclei to form larger nuclei

    o Problems in harnessing energy in a controlled way

    o No commercial use

    ; Biomass:

    ; Fuel produced by biological processes

    ; Energy from Sun through photosynthesis (6CO(g) + 6HO(l) CHO(s) + 6O(g)) 2261262

    ; Burning plant materials reverses process, releasing energy

    ; Fermentation of starch and sugars ethanol

    ; Renewable

    ; Not enough energy for demands of modern society

    ; Electrochemical cells:

    ; Difference in redox potential flow of electrons

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    ; Portable source of energy

    ; Stores limited amounts of energy

    ; Solar energy:

    ; Non-polluting

    ; Freely available during daylight hours

    ; Harnessed by solar heating panels direct storage of energy

    ; Photovoltaic cells convert solar energy into electricity ; Other energy sources:

    ; Renewable

    ; Not harnessed efficiently

    ; Wind power, wave power, hydroelectric power drive generator

    ; Tidal energy:

    o harnessed from gravitational force between Earth and Moon

    o only generated when there is tidal movement

    ; Geothermal energy:

    o Heat stored in the interior of the Earth

    o Generated by gravitational forces + natural radioactivity

    F.2 Fossil Fuels (4h)

    F.2.1 Describe the formation and characteristics of coal, oil and natural gas.

    ; Coal

    ; Formation:

    o Fossilized plant material

    o Carboniferous period

    o Pressure + Heat causes plant material peat lignite sub-bituminous

    soft coal bituminous soft coal hard coal

    o Percentage of carbon increases at each stage

    ; Characteristics:

    o Readily combustible

    o 40-98% carbon + volatile materials + moisture

    o Made up of elements H, O, N, S

    o Analysis on basis of water content, mineral impurity, volatile materials, fixed

    carbon content

    ; Petroleum/Crude Oil

    ; Formation:

    o Remains of marine organisms

    o Paleozoic period

    o Sediments built up on top of organic layers

    o High pressure + biochemical activity

    o Collected in traps

    ; Characteristics:

    o Dark, foul-smelling liquid

    o Straight-chain + branched + cyclic + aromatic hydrocarbons

    o N, O, S in small quantities

    o Liquid easy to transport

    ; Natural Gas

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    ; Formation:

    o Formed from the decomposition that produced crude oil and coal

    ; Characteristics:

    o Mainly methane (85-95%), ethane, propane, butane

    o Scarce supplies

    F.2.2 Determine and compare the enthalpies of combustion of coal, oil and natural gas.

    ; Heat evolved when one mole of a substance is completely burnt in oxygen

    ; To calculate, need:

    ; Known mass of substance being burned

    ; Temperature change of known mass of water

    ; Specific heat of water

    ; Specific heat of calorimeter

    ; Mass of calorimeter

F.2.3 Outline the composition and characteristics of the crude oil fractions used for fuel.

    Fractions Carbon Chain Length Boiling Point Range Major Uses

    Gaseous Fuels for automobiles, 0-20

    Hydrocarbons cooking, domestic + 1-4

    industrial heating (gases)

    Petroleum Ether / Solvents for varnishes, 20-100

    Naphta dry cleaning, cracking 5-7

    stock for methane (liquids)

    Gasoline Fuels for internal 40-175

    combustion engines 5-12 (readily vaporize in

    car engines)

    Jet engine and diesel Kerosene Oil

    fuel 175-300

    12-18

    (liquids)

Gas Oil / Diesel Oil Diesel fuel, cracking 300-400

    stock to produce 18-24

    gasoline (liquids)

    Lubricating Oil / Wax Lubricants, cracking

    stock Oil / Greases 20-30 Non-volatile

    Paraffin Wax Candles, packaging,

    High boiling point polishing wax, 25-40 (solids) petroleum jelly, water

    proofing

    Asphalt, roofing, water Residue, bitumen High boiling point >30 proofing (solids)

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    F.2.4 Describe how the components of a hydrocarbon fuel relate to its octane rating.

    ; Octane rating is a measure of the ability of a fuel to resist 'knocking' when burnt in a

    standard test engine.

    ; A fuel is rated relative to heptane (rating of 0, poor fuel) and 2, 2, 4-trimehylpentane (rating

    of 100, rich fuel).

    ; More straight chain lower octane rating

    ; Addition of organo lead compounds improves octane rating, highly toxic ; Replaced by addition of aromatic compounds

    F.2.5 Explain the processes of coal gasification and liquification. ; Coal gasification:

    1. Hydrogasification (high temperature and pressure):

    C+ HO ? CO + H (+ impurities) (coal) 2(g)(g)2(g)

    2. Catalytic increase of H: 2

    CO + HO ? CO + H (g)2(g)2(g)2(g)

    3. Removal of impurities:

    CO + HO + HS (oxidized to sulfur and sold as a by-product) 222

    4. Catalytic Methanation (reverse of Haber process):

    3H + CO ? CH + HO 2(g)(g)4(g)2(g)

    5. Removal of HO: 2

    Leaves high energy value methane fuel, Synthetic Natural Gas

    ; Coal Liquification:

    1. Hydrogasification

    2. Fischer-Tropsch Method (products passed over iron/cobalt catalyst)

    CO + H ? HCHO ; methanal (g)2(g)(g)

    HCHO + H ? CHOH ; methanol (g)2(g)3(l)

    Amount of hydrogen determines if it is alkanal or alkanol

    F.2.6 Describe how the burning of fossil fuels produces pollutants. ; The primary pollutants are CO, CO, SO, NO, particulates (fly ash) and hydrocarbons. 22x

    ; Sulfur:

    ; Present in coal and oil

    ; S + O ? SO (s)2(g)2(g)

    ; 2SO + O ? 2SO 2(g)2(g)3(g)

    ; SO + HO ? HSO 3(g)2(l)24(aq)

    ; Acid rain

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; NO: x

    ; High temperatures at which fossil fuels are burned oxides of nitrogen form

    ; React to form NO nitric acid acid rain 2

     breakdown to form oxygen radicals and then secondary ; Photochemical smog

    pollutants, such as ozone + PANs ; Particulates (fly ash):

    ; Coal and carbon particles in incomplete combustion of gasoline and diesel

    ; CO:

    ; Incomplete combustion

    ; Hydrocarbons:

    ; Form when petroleum fuels evaporate

    ; Carcinogenic and volatile

    ; CO: 2

    ; Combustion of natural gas

    ; Greenhouse gas global warming

    F.2.7 Discuss the advantages and disadvantages of the different fossil fuels.

    Fossil Fuel Advantages Disadvantages

    1. Large quantities 1. Acid rain + Global warming

    2. Well-distributed 2. Not so readily transported

    3. Converted into synthetic liquid 3. Waste ground acidity + visual and

    fuels and gases chemical pollution

    4. Yields far more energy than 4. Mining is dangerous Coal renewable sources 5. Dirty

    5. Safer than nuclear power

    6. Longer life span than oil or gas

    7. Feedstock for organic chemicals

    1. Easy transportation 1. Acid rain + Global warming

    (pipelines/tankers) 2. Limited lifespan

    2. Use in cars, lorries, etc. 3. Uneven distribution Oil

    3. Feedstock for organic chemicals 4. Risk of pollution during transportation

    1. Clean fuel 1. Global warming

    2. Easily transported (pipelines, 2. Limited lifespan

    pressurized containers) 3. Uneven distribution

    3. Does not contribute to acid rain 4. Risk of explosions due to leaks Natural Gas

    4. Higher quantity of energy per kg

    than coal or oil

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F.3 Nuclear Energy (4h)

    F.3.1 Distinguish between nuclear reactions and chemical reactions.

    ; Nuclear reactions nuclei are converted to other nuclei, mass is converted into energy

    ; Chemical reactions valence shell electrons are rearranged as bonds are broken or formed F.3.2 Write balanced nuclear equations.

     Both the atomic number and mass number must be balanced.

F.3.3

     Compare the charge, mass, penetrating power and behaviour in an electric field.

    Relative Penetrating Behavior in Name Type Mass / amu Charge power Electric Field

    A few cm of Deflected Helium nucleus Alpha air. Stopped 4 +2 toward the 2+ Particle (α) by paper, skin negative plate or clothing.

    Greater

    A few m of air. deflection Electron Beta Particle Stopped by toward the -1 (β) thin positive plate aluminum (less

    masseous)

    A few km of

    air. Stopped High energy Gamma by 10 cm of electromagnetic 0 0 No deflection Radiation (γ) lead or radiation several m of

    concrete

F.3.4 State the concept of half-life.

    ; Half-life is independent of the amount of a radioactive sample.

    ; Time required for one-half of the initial substance of radioactive material to decay. F.3.5 Apply the concept of half-life in calculations.

     Restrict this to whole number of half-lives.

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    F.3.6 Compare nuclear fission and nuclear fusion.

    ; Nuclear fission:

    ; Splitting of a heavy nucleus into two or more lighter nuclei with the simultaneous

    release of neutrons and large amounts of energy.

    ;

    ; Nuclear fusion:

    ; Brings together nuclei of two lighter elements to form a heavier nucleus with the

    release of energy.

    ;

    F.3.7 Explain the functions of the main components of a nuclear power plant. ; Reactor produces heat from a nuclear reaction

    ; Turbine drives a generator to produce electricity

    ; Shield concrete container in which Uranium and Plutonium are housed ; Fuel rods contain fissionable material

    ; Moderators slow down the neutrons, making them more likely to collide with the

    fissionable nuclei; made of an inert material (water/graphite) ; Control rods controls the chain reaction, lowered or raised to absorb excess neutrons;

    made of cadmium or boron

    ; Primary coolant controls and extracts heat produced, water at high pressure (primary

    coolant), liquid sodium, air, heavy water, carbon dioxide

    ; Secondary coolant provides steam to turn blades of the turbine, avoids the transfer of

    radioactive material to the water used to power the generator

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F.3.8 Discuss the differences between conventional power generation and nuclear reactors.

     Differences

    Similarities Conventional Power Nuclear Reactors

    1. Generators to produce 1. Ordinary chemical 1. Nuclear combustion to

    electricity combustion reaction to produce heat from mass 2. Turbines produce heat defect

    3. Thermal power 2. Fuel does not have to be 2. U-235 fuel has to be 4. Cooling tower enriched by complex enriched

    methods 5. Thermal pollution

    3. Fuel rods in an airtight

    building; neutrons cause

    fission 3. Fuel burnt in a furnace;

    4. Requires containment requires air

    building to isolate

    radioactive fuel 5. Uses two heat transfer

    loops a primary to carry 4. Requires no containment heat from the reactor and a building secondary where steam is

    produced 6. Products can be highly

     radioactive but no CO25. Requires only one produced (primary) heat transfer

    loop or cycle

     7. About 30% unspent fuel unusable. Spent fuel highly

    radioactive 6. Products are CO 28. Used fuel rods require (greenhouse gas) + SO 2expensive reprocessing; (very little from natural accidents can release gas) + particulates radioactive materials 7. All fuel can be used up 9. Failure of control or cooling

    system can lead to melt down

    10. Nuclear waste has to be stored and eventually

    disposed of 8. SO can be removed using 2

    scrubbers and particulates

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    using electrostatic

    precipitators

    9. No melt down possible

    10. Fly ash can be used in road

    making

F.3.9 Discuss the concerns about safety in nuclear power plants.

    ; Possibility of a meltdown:

    ; Nuclear reactor becomes out of control

    ; Neutrons are absorbed by non-fissionable material in theory, not enough

    momentum for a spontaneously explosive chain reaction

    ; Escape of radioactive material:

    ; Occurs during transportation or usage of fuel

    ; Fire igniting the moderator can cause radioactive gas to spread

    ; Transfer of low level waste by ordinary materials (surrounding air, clothes)

    ; Escape of the coolant:

    ; Fast breeder reaction sodium metal

    ; Reaction with water disastrous

    ; Nuclear waste:

    ; Must be stored for hundreds to thousands of years before becoming harmless

    ; Vitrifying the waste in glass and burying it deep underground

    ; Disruption by earthquakes or slow seepage of the waste

F.4 Solar Energy (3h)

F.4.1 State how solar energy can be converted to other forms of energy.

    ; Photosynthesis chemical energy biomass

    ; Passive and active space heating thermal energy - heat

    ; Photovoltaic cells electricity

    ; Wind and water power electricity

    F.4.2 Describe the role of photosynthesis in converting solar energy to other forms of energy.

    ; 6CO+ 6HO ? CHO + 6O 2(g) 2(l)6126(s)2(g)

    ; Endothermic

    ; Products can be used for food, fermented into ethanol, or burned for heat

    F.4.3 Discuss how biomass can be converted to energy.

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; Direct combustion:

     ; CHO + 6O? 6CO+ 6HO 6126(s)2(g) 2(g)2(l)

    ; Advantage low cost

     greenhouse gases ; Disadvantage

    ; Combustion of waste materials from other processes:

    ; Animal and plant waste are burned in incinerators, providing heat + electricity

    ; Advantage reduces waste in landfill sites

    ; Disadvantage greenhouse gas

    ; Production of biogas:

    ; Anaerobic decay of organic matter by bacteria methane + carbon dioxide

    ; Advantage Heating, cooking and refrigeration of rural communities

    ; Disadvantage greenhouse gases, only small amounts of energy ; Production and use of ethanol:

    ; Fermented: CHO ? 2CHOH + 2CO 6126(s)25(l)2(g)

    ; Burned: CHOH + 3O ? 2CO + 3HO 25(l)2(g)2(g)2(l)

    ; Ethanol + gasoline gasohol cars less reliant on pure gasoline ; Biofuels:

     renewable, readily available, relatively non-polluting ; Advantages

    ; Disadvantages take up land, remove nutrients from soil, widely dispersed

    F.4.4 Outline the principles of using solar energy for space heating. (Storage of heat by water and

    rocks)

    ; Passive space heating:

    ; Well-insulated homes with windows facing a sunny aspect

    ; Low installation and running costs

    ; Depends upon a plentiful supply of sunlight

    ; Needs a back-up energy supply

    ; Active space heating:

    ; Energy absorbed using black bed collectors

    ; Heated air/water is pumped into storage tanks containing water or rocks

    ; Pumps and fans distribute the stored heat when required

    ; Installation more expensive than passive heating

    ; Energy available to do work is lost each time the energy is converted

    F.4.5 Discuss the methods for converting solar energy into electricity. ; Parabolic mirrors:

    ; Concentrate the Sun’s rays to heat up oil or liquid sodium

    ; Liquid is pumped to a heat exchanger converting water to steam

    ; Quick to build the set-up

    ; Free and limitless fuel supply

    ; Non-polluting

    ; Large areas of mirrors

    ; Work best in deserts

    ; Surfaces need to be able to endure extremes of temperature

    ; Constant attention to keep surfaces clean

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