Developing Fuels - Pollutants Flashcards
What primary pollutants can be produced by incomplete combustion in engines?
NOx
SO2
Unburned hydrocarbons (CxHy)
CO
C particulates
Which pollutants does diesel produce more of?
Carbon particulates and unburned hydrocarbons as bigger hydrocarbons are used in diesel
What are the effects of CO if it is inhaled?
It binds to the haemoglobin in the blood causing a lack of oxygen for respiration. Can be fatal.
How is NO produced in an engine?
When the engine heats up, it causes the N and O in the air to react to form NO
What are the effects of NO?
Reacts with water in clouds to produce nitric acid which causes acid rain
This can damage statues, buildings and kill wildlife
It also causes respiratory issues when inhaled and is a greenhouse gas
How is photochemical smog produced?
When a mixture of pollutants are released in a condensed area
What are the effects of photochemical smog?
Blocks sunlight
Produces secondary pollutants
What are secondary pollutants?
Pollutants formed by primary pollutants eg ozone
How is ozone formed as a pollutant?
produced in photochemical smog
How is sulpher dioxide formed as a pollutant?
sulpher present in crude oil reacts with the oxygen in the air when hot enough
What are the effects of SO2?
same as NO:
acid rain
greenhouse gas
toxic
How can sulpher dioxide polluting be prevented?
By using low-sulpher fuels
Mainly an issue with diesel and coal
What is the purpose of catalyctic converters in engines?
It converts NO and CO into CO2 and N2
What catalyst is used in catalyctic converters?
Pt/Rh alloy - known as ‘honeycomb’
What is the reaction for the conversion in catalytic converters?
NO + CO -> CO2 + 0.5N2
What are the issues with catalytic converters?
must be hot -> most NO and CO is produced before the engine is hot enough for the converter
finite lifetime as it is poisoned by unburnt carbon
What are some alternative fuels for petrol and diesel?
Hydrogen
Biofuels
Biodiesel
Electric
What are biofuels?
Usually ethanol from the fermentation of sugars
What are the benefits of biofuels?
higher energy density than hydrogen
near;y carbon neutral
What are the drawbacks of biofuels?
uses land that could be used for feeding people
absorbs moisture which leads to corrosion
lower energy density than biodiesel, petrol and diesel
How is hydrogen used to fuel engines?
2H2 + O2 -> 2H2O
reacts with oxygen to produce water
What are the benefits of hydrogen as a fuel?
doesn’t produce pollutants other than NO
doesn’t release any carbon back into the atmosphere
What are the drawbacks of using hydrogen as a fuel?
low energy density
issues with distribution and refueling - rare to find refuel stations
explosive
still get NO
extracted from natural gas (still releasing pollutants) or from electrolyisis (needs electricity)
What is can biodiesel be made from?
waste that would otherwise go to landfill
