Chapter 1 Fuels Flashcards
Define a ‘fuel’
- What form is fuel usually stored in?
- What is energy produced as a result of?
Fuels are substances with stored chemical energy that can be released relatively easily for use as heat or power to carry out a specific function.
- stored energy is either in chemical or nuclear form
- produces energy due to the chemical/nuclear reactions
What are the two categories of fuels?
- Fossil fuels
- Biofuels
Define a ‘fossil fuel’
Fuels that have been produced over a long period of time by the breakdown of organic material where such process can take hundreds of thousands of years.
Give examples of fossil fuels
- coal
- crude oil
- natural gas
- liquefied petroleum gas (LPG)
Define the term ‘non-renewable’
Resources that are used faster than they are replaced, and cannot be replenished in a person’s lifetime and are thus finite. (Resources are limited -finite- and will eventually be exhausted)
Describe the formation of fossil fuels and name the process
Process is called FOSSILATION - produced by the fossilisation of dead plant and animal matter
- dead organism is buried in low oxygen conditions, which prevents the break down of the organism’s body
- multiple layers of rock and landform over the dead organic material, subjecting it to extremely high heat and pressure over millions of years.
- Above leads to the formation of solid coal, liquid crude oil and natural gas
True or false, “organic matter does not retain any of its chemical energy”
False.
Organic matter retains some of its chemical energy which plants originally accumulated when carrying out photosynthesis.
Detail the environmental impacts of coal (sourcing)
- Land clearance to mine for coal damages wildlife habitat and affects their ecology.
- Water contamination: heavy metals and minerals in the rock dissolve in mine waste-water may seep into the table and our source of drinking water.
- Miners themselves are at health risks. They breathe in coal dust which contains particulates and can end up getting pneumoconiosis (lung cancer)
Detail the environmental impacts of coal (combustion)
- production of the greenhouse gases such as CO2 accelerate the enhanced greenhouse effect and contributes to climate change.
- Production of acidic gases such as NO, NO2 and SO2 which dissolve in water to form acid rain.
- Nitrogen oxides react with the air at ground level using sunlight and a catalyst to form ozone (O3), a toxic gas that results to photochemical smog
- burning coal forms particulates which contribute to air pollution and smog resulting in serious human health issues.
Explain the process of fractional distillation
For more info:
https://science.howstuffworks.com/environmental/energy/oil-refining4.htm
- Involves a fractionating column
- Components are separated on the basis of a boiling point and molecular size.
- Utilises heat to separate components of a mixture to a number of fractions.
- Heat the mixture of two or more substances with different boiling points to a high temperature.
- Mixture boils and forms vapour
- Vapour enters the bottom of the column that is filled with trays. These trays have bubble caps in them which allow the vapour to pass through.
- vapour rises in a column
- Vapour rises and cools
- When a substance in the vapour reaches a height where the temperature of the column is equal to that substance’s boiling point, it will condense to form a liquid. (The substance with the lowest boiling point will condense at the highest point in the column; substances with higher boiling points will condense lower in the column.).
- The trays collect the various liquid fractions.
- The collected liquid fractions may pass to condensers, which cool them further, and then go to storage tanks, or they may go to other areas for further chemical processing
Effect of bonding on fractional distillation of crude oil,
The boiling point of molecular substances is dependent on the strength of the intermolecular forces.
- Non polar alkanes - only have dispersion forces
- Dispersion forces increase with increasing mass
- Thus lighter alkanes condense ar the top of the column whereas heavier alkanes condense near the bottom
Environmental impacts of crude oil (sourcing)
- habitat destruction due to land clearing when crude oil is extracted via drilling. But it is not as bad as the land clearing when mining coal.
- relates to fracking, Water used to fracture the rock often dissolve heavy metals and toxic substances that can seep through to the water table and our aquifer.
- oil spillages below the seabed result are toxic to marine animals, leading to a number of ecological impacts.
Environmental impacts of crude oil (combustion)
- burning of crude oil releases CO2 accelerating the enhanced greenhouse effect
- produces acidic gases, NO, NO2 and SO2 which contribute to acid rain.
- Formation of ozone leads to photochemical smog
Natural gas found in coal deposits is called….
coal seam gas
Natural gas found in shale rock is called….
Shale gas
Environmental impacts of natural gas (sourcing)
- habitat destruction in the clearing of surrounding the land
- gas leakage, especially of methane, which is an even better heat-trapping GHG
Environmental impacts of natural gas (combustion)
- production of CO2
- production of acidic gases
Environmental impacts of CSG (sourcing)
- habitat destruction
- gas leakage
- contamination of water supply
- depletion of water supply
Environmental impacts of CSG (combustion)
- production of CO2
- production of acidic gases
Define a “biofuel”
A fuel that can be produced from crops or other organic material. Examples of biofuels are ethanol from the fermentation of sugars, methane from animals and biogas from plant and animal waste material.
Can be used alone or mixed in petrol
Define the term “renewable”
Resources derived from natural processes and are used at the same rate that it is produced. Thus, these sources can be replenished in a short time and are hence infinite.
List types of biofuels
- bioethanol
- biodiesel
- biogas
Formula for formation of bioethanol
C6H12O6(aq) ->2CH3CH2OH(aq) + 2CO2(g)
yeast on the arrow
Environmental impact of bioethanol (sourcing)
- habitat destruction
- depletion of our food sources in an attempt to minimise land clearance
Environmental impact of bioethanol (combustion)
- not 100% carbon neutral. Including indirect CO2 emissions, bioethanol has a net production of CO2 into the atmosphere.
Describe a transesterification reaction
The process by which triglycerides are converted to FAMEs.
- . Triglyceride is mixed with KOH and is dissolved in methanol by warming it.
- In this reaction, the triglyceride is converted to a small molecule called glycerol and 3 ester molecules with long carbon chain. The ester molecules are the biodiesel product.
Environmental impact of biodiesel (sourcing)
- habitat destruction
- depletion of our food sources in an attempt to minimise land clearance
Environmental impact of biodiesel (combustion)
- not 100% carbon neutral. Including indirect CO2 emissions, bioethanol has a net production of CO2 into the atmosphere.
Environmental impacts of biogas (sourcing)
- when sourced from biomass = land clearance, habitat destruction, land loss
- loss of land used to produce food.
Environmental impacts of biogas (combustion)
- CO2 is the main product of biogas consumption, a GHG
What do all substances have?
All substances have chemical energy which is referred to as the energy content.
What happens when fuels are used?
Energy is converted to a different form of energy
Define the term “energy transformation”
Energy is converted from one form to a different form where total energy remains unchanged (as the law of conservation of energy states)
Define the term “energy efficiency”
Describes the percentage of energy from a source that is converted to useful energy.
How is energy harnessed from most fuels
Through combustion
Complete combustion products
CO2 and H20
Incomplete combustion products
CO, C (either) and H20
ELECTRICITY FROM COAL
- Formula
- Transformations
- Energy released
- efficiency
1. C(s) + O2(g) -> CO2(g) 2. chemical -> thermal energy thermal(Coal) -> thermal (steam) thermal (steam) -> mechanical mechanical -> electrical 3. 32 kJ/g 4. 30-40%
ELECTRICITY FROM NATURAL GAS
- Formula
- Energy released
- efficiency
- CH4(g) + 202(g) -> CO2(g) +2H20(l)
- 890KJ for one mole of methane
- 40% efficency
ELECTRICITY FROM BIOGAS
- Formula
- Energy released
- CH4(g) + 2O2(g) -> CO2(g) + 2H20(l)
2. less than that of natural gas
ELECTRICITY FROM LPG
- Formula
- Energy released
- efficiency
- C3H8(G) +5O2(g) -> 3CO2(g) +4H20(l)
FUELS FOR TRANSPORT
- Formula
- content
- efficency
- crude oil is used most often
- petrol, a mixture of hydrocarbons including octane is vital.
C8H18(aq) + 25O2(g) -> 3CO2(g) + 4H20(l)
2. content = 50.5kj/g
Define the term ‘carbon neutral’
A process that absorbs the same amount of carbon as it generates. The CO2 absorbed from the atmosphere by a carbon neutral process compensates for the CO2 produced by the process.
Petrodiesel
- obtained from the fractional distillation of crude oil
- impure
- compostion is usually 75% alakanes, 25% aromatic hydrocarbons but changes based on the manufactuerer.
- alkanes - C10-C15
Comparing biodiesel and petrodiesel (Combustion)
BOTH
- both contain mostly carbon atoms, so CO2 is a major combustion product
DIFF
- biodiesel produces less CO and NOx oxides
- biodiesel contains less sulphur than petrodiesel and forms less S02
Comparing biodiesel and petrodiesel (flow along fuel lines)
DIFF
- biodiesel is more viscous than petrodiesel due to the presence of additional dipole-dipole bonds
- biodiesel is more hydroscopic than petrodiesel because it can form hydrogen bonds with water molecules using its C–O group as a h-bond acceptor
Comparing biodiesel and petrodiesel (environmental impacts)
Biodiesel leads to:
- less production of CO
- lower emissions of paticulates
- lower emissions of unburnt hydrocarbons
- higher emissions of nitrogen oxides
- carbon neutral
- comparable (albeit lower) emissions of SO2
Comparing biodiesel and petrodiesel (Structure)
Biodiesel - polar and asymmetrical
Petrodiesel - non-polar, linear hydrocarbon chain
Comparing biodiesel and petrodiesel (Renewability)
Biodiesel - renewable
Petrodiesel - non-renewable
Comparing biodiesel and petrodiesel (energy content)
Biodiesel has a lower energy content (41Kj/g) than petrodiesel (48Kj/g)
Comparing biodiesel and petrodiesel (cloud point)
Biodiesel reaches it cloud point earlier - forms small crystals - than petrodiesel
Bio = -3 to 12 degrees celcius
pet = -15 to 5 degrees celcius
Comparing biodiesel and petrodiesel (cold flow)
Petrodiesel can be used without additives at lower temperatures whilst biodiesel requires antifreeze additives in cold conditions/climates
Define the fuel “coal”
A fossil fuel that is composed of a variety of very large hydrocarbon molecules that can be combusted to release energy to generate electricity
State coal’s renewability
Non-renewable
Describe coal’s composition
Mostly carbon, hydrogen, nitrogen, sulphur and a few other elements
State how coal is formed
Via fossilisation.
Contrast, peat, brown and black coal (% of carbon)
Peat has the lowest percentage carbon (60%) followed by brown coal (70%) and then black coal (90%).
Contrast peat, brown and black coal (energy content)
Peat also has the lowest energy content (17kJ/g) followed again by brown coal (20kJ/g) and black coal (32kJ/g)
Contrast peat, brown and black coal (production)
Peat is produced under lowest pressure/heat and black coal with most.
Contrast peat, brown and black coal (fuel quality)
Peat is the lowest fuel quality, whilst black has the best.
Contrast peat, brown and black coal (heat release and water content)
Peat releases the least heat and has the most water (vice versa for black coal)
Why does coal with a lesser heat content releases more water?
A part of the energy is absorbed by the water molecules in order to evaporate it, and thus, the energy accounted for is less.
Define the fuel “crude oil”
A mixture of hydrocarbon molecules that are mostly members of the homologous series of alkanes.
State crude oil’s renewability
Non renewable
Describe crude oil’s composition
Alkanes
Detail crude oil’s formation
Fossilisation
Describe its extraction process
Crude oil itself has no use as a fuel, but it contains many useful components. Therefore, it must be refined to be used as a fuel via fractional distillation.
Define the fuel “natural gas”
A fossil fuel found in deposits in the earth’s crust mainly comprised of methane, together with smaller hydrocarbons such as ethane and propane.
State natural gas’ renewability
Non-renewable
Describe natural gas’ composition
Mostly methane, with small %s of propane, ethane, water, sulphur, CO2 and nitrogen
Detail natural gas’ formation
fossilisation
Detail extraction process
Drilling
Define Liquefied Petroleum Gas (LPG)
A mixture of propane and butane which is separated from natural gas or crude oil and stored under pressure to liquefy the propane and butane
State LPG’s renewability
Non-renewable
Describe LPG’s composition
Propane and Butane
Detail LPG’s formation
It is produced as a by-product of natural gas processing and petroleum refining.
Define coal seam gas (CSG)
Natural gas trapped by pressure on the surface of a coal seam.
State CSG’s renewability
Non-renewable
Derail CSG’s composition
Mostly methane
Define bioethanol
Ethanol that is made by fermenting the sugar and starch components of plants using yeast.
State bioethanol’s renewability
Renewable
Describe bioethanol’s composition
Ethanol (C2H5OH)
Detail bioethanol’s formation
Via fermentation of glucose by yeast cells. Enzymes catalyse the breakdown of starch in grain crops to glucose whilst other enzymes in yeast then convert glucose and other small sugar molecules to ethanol and carbon dioxide.
Detail bioethanol’s formation
Via fermentation of glucose by yeast cells. Enzymes catalyse the breakdown of starch in grain crops to glucose whilst other enzymes in yeast then convert glucose and other small sugar molecules to ethanol and carbon dioxide.
Define biodiesel
A fuel derived from vegetable oil or animal fat, consisting of long-chain alkyl esters. Biodiesel is typically made by reacting triglycerides with an alcohol.
State biodiesel’s renewability
Renewable
Describe biodiesel’s composition
A mixture of fatty acid methyl esters (FAMEs)
Detail biodiesel’s formation
Transesterification reactions.
Define biogas
A mixture of gases produced by the breakdown of organic matter in the absence of oxygen by anaerobic bacteria.
State biogas’ renewability
Renewable
Describe biogas’ composition
Primarily methane with a significant amount of CO2 but the composition of biogas is dependent on the original material from which it is obtained and the method of decomposition.
