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NFCRC Tutorial: Fossil Fuels

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Fossil Fuels Natural gas, oil and coal are the three (fossil) fuels that are abundantly used. These fuels are remains (fossils) of life forms such as marine organisms and plant life, that flourished on our planet millions of years ago. This energy is thus a stored form of solar energy that accumulated over millions of years, and at the current and projected rates of consumption, fossil fuels will be used up in a fraction of time compared to the time it took to collect the energy from the sun.


photo of fossils of marine organisms which can be used for fuel

Natural gas as supplied is the cleanest fuel with sulfur removed (except for small amounts of odorants added), no ash and only molecular nitrogen, and a high hydrogen to carbon (H/C) ratio which minimizes the greenhouse gas CO2 emission. Coal is the worst (dirtiest) containing sulfur, elemental nitrogen, low H/C ratio and ash, while oil represents an intermediate fuel in terms of quality. The U.S. has abundant reserves of coal, enough to meet its energy demands for the next 300 years. Natural gas is simplest in terms of composition and being a gas mixes immediately in the combustor, while coal has a very complex structure and being a solid is more difficult to burn. Coal combustion undergoes devolatilization and combustion of the released gases, char combustion and fly ash formation which are particles 10 microns in size (the low visibility around certain coal fired power plants is due to the fly ash). Oil which contains more than 300 molecular species needs to be atomized (less than 10 microns to provide large surface area), and within the combustor it has to vaporize and mix before combustion can occur).

Quiz

1. Which of the three fossil fuels (Natural Gas, Coal, & Oil) is the cleanest fuel and simplest in terms of composition?
a) Natural Gas
b) Coal
c) Oil

2. Dinosaur bones can be used as fuel.
a) true
b) false
c) don't know

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