Introduction to fuels Flashcards
Energy
Energy is the ability to do work. Unit of energy is joule, J. Larger amount of energy can be expressed as kJ (1000J), MJ (megajoule, 10^6 J) or GJ (gigajoule, 10^9 J
What are fuels?
Fuels are substances that can produce energy for heat or power through combustion reactions (as fossil fuels) or through disintegration such as decaying of nuclear fissions or through combination such as nuclear fusions.
This broadly divides fuels into 2 groups: (i) non-renewable fuels (ii) renewable fuels.
What is the level of impact of fuels on society?
The use of fuels in society and their impact are considered at a local, national or global level. Choices about fuels used locally have an impact regionally or globally. How and which fuels are used are decided by global and national governments. They take into account the sustainability of specific fuels to determine their long-term impact.
What are the 2 broad groups which fuels are classified as? Give examples of the types of fuels in these categories.
Fuels can be classified into 2 major categories: non-renewable energy resources (fossil fuels + uranium) and renewable energy resources.
Non-renewable energy resources are considered to be exhaustible because they are being used at a faster rate than they are being replaced. e.g. coal, crude oil (petroleum), natural gas and uranium.
Renewable energy resources are considered to be able to last indefinitely without any reduction to their supply as they do not rely on finite resources. e.g. solar energy, hydroelectricity, wind power, tidal power, geothermal power, firewood and the use of biogas.
How are fossil fuels created and why are they a non-renewable source?
Most of the energy used for heating, electricity generation, and powering vehicles all come from burning fossil fuels in coal-fired power stations.
Fossil fuels are formed from the ancient remains of plants, animals and microorganisms that have undergone intense heat and pressure underground. They take millions of years to make, therefore once we run out, we will not be able to make anymore. They are a non-renewable source.
What is sustainability? What is a sustainable fuel?
It refers to the ability to be maintained at a certain rate or level. A sustainable fuel is one which is able to support energy and resources into the future without depletion.
What is coal and how is it formed?
Coal is formed from wood and other plant material. Over time a gradual chemical change occurs in the wood - the proportion of hydrogen and oxygen (water) decreases, and carbon increases. The wood becomes peat, brown coal, and then black coal. Coal is a mixture of large molecules made from carbon, hydrogen, nitrogen, sulfur, and other elements.
How does peat, brown coal and black coal compare and what factors lead to peat forming brown coal and eventually black coal?
Black coal is a better fuel than peat or brown carbon, as it has a higher percentage of carbon. The process where peat becomes brown coal than black coal is one where there is an increase in the fuel quality. Peat changes as the time, pressure and temperature increases.
Peat: 60% carbon (40% H2O and other parts), Heat released is 25kJ/g
Brown coal: 70% carbon, Heat released is 30kJ/g
Black coal: 90% carbon, Heat released is 35kJ/g
(note: the heat is released when combustion occurs and the values are for dried coal)
What is crude oil and how is it processed to increase its usefulness?
Crude oil, or petroleum, is a mixture of hydrocarbon molecules that are mostly members of the alkane homologous series. Crude oil must be separated into its constituents in order for it to be useful as a fuel. This is done through the process called “Fractional Distillation”. Each separated fraction (each fraction contains different/specific lengths of carbon chains) can be used as fuels or refined further.
What is natural gas, where is it found, how is it extracted (impact of this on the environment)?
Natural gas is found in deposits in the Earth’s crust. It is composed of mostly methane, along with small amounts of other small hydrocarbons. Natural gas can be found:
- In gas reservoirs between layers of rock
- As a component of crude oil
- In coal deposits where it is bonded to the surface of the coal. This is known as coal seam gas (CSG).
- Trapped in shale rock. This is known as shale gas.
Natural gas from coal or shale deposits are usually extracted through a process known as fracking. There is a huge concern about the impact of fracking on the local environment and underground water supplies.
What is fracking?
Sand, water and other chemicals are injected into the deposit at high pressure (into the well) to free the natural gas from coal or shale.
How can fractional distillation be used with natural gas?
It can be used to separate propane and butane gases from natural gas. When under pressure the gases (propane and butane) become liquids and are sold as liquefied petroleum gas (LPG). This can be used as fuels in cars, or in homes for heating and cooking.
C1 - C4
Refinery gas: LPG, feedstock for chemical industry
A feedstock refers to any unprocessed material used to supply a manufacturing process. In chemistry, a feedstock is a chemical used to support a large-scale chemical reaction.
C5 - C7
100C
Naphtha: chemical industry
Naphtha is a flammable liquid made from distilling petroleum. Naphtha is used to dilute heavy oil to help move it through pipelines, to make high-octane gas, to make lighter fluid, and even to clean metal.
C8 - C12
250C
Petrol: motor fuel
