DF 11 - other fuels Flashcards
specification reference - (k) (u)
how else can we tackle the problem with emissions
to use an alternative fuel for the car
how much of petrol do aromatic hydrocarbons make up
40%
what can aromatic hydrocarbons cause
higher carbon monoxide, hydrocarbon and nitrogen oxide emissions and some may cause cancer
which aromatic hydrocarbon usage is strictly controlled
benzene
why is butane content likely to be lowered in the future
butane is volatile and responsible for evaporative emissions leading to ozone formations and photochemical smogs
what do butane and aromatic hydrocarbons help petrol to do
perform well in modern engines
what do petrol companies plan to replace aromatic hydrocarbons and butane with
oxygenates
what are oxygenates
compounds containing oxygen
what is liquid petroleum gas called when used in cars
autogas
where does liquid petroleum gas come from
the distillation of crude oil
what is LPG made of
mixture of propane and butane in varying quantities. often 60% propane
what must happen for hydrocarbons to be used as liquids
they have to be kept under pressure
why do petrol vehicles need a larger fuel tank
so that the vehicle can run on more than one fuel
where does autogas work
in high performing engines and produces 20% less CO2 per mile than petrol. it also produces fewer unburnt hydrocarbons and nitrogen oxides than petrol
why does autogas release less carbon monoxide
because of the higher ratio of carbon to hydrogen
what is the advantage of using autogas
for vehicle owners, road and fuel taxes are lower for petrol
what is the disadvantage of using autogas
LPG filling stations are rare although numbers are increasing
what is liquid natural gas mainly made up of
methane and comes from oil and natural gas fields
how is methane liquefied
it cant be liquefied by pressure alone and must be cooled to below -160°
why is LNG suitable for larger vehicles
it works in modified diesel engines
what is the good thing about LNG
it has a high C:H ratio so less CO is produced and much fewer NOx than diesel
what do schemes for developing alternating fuels for use on large scale depend on
long term and large scale investments in new infrastructure/ it depends on political and economic factors
give alternatives to fossil fuels
biofuels, ethanol, biodiesel and hydrogen fuels
what are biofuels and give examples
alternative feusl derived from renewable animal and plant materials. examples include ethanol and biodiesel
what is ethanol made from
fermentation of carbohydrate crops such as sugar cane
why cant cars easily run on ethanol alone
it is too volatile
what is used instead of using pure ethanol
mixtures of petrol containing 15% ethanol
why is ethanol said to be carbon neutral
carbon dioxide is produced in fermentation and burning the ethanol matches the carbon dioxide absorbed in the growing plant.
how is ethanol distributed
energy is used to produce and distribute ethanol producing carbon dioxide if the energy comes from fossil fuels.
what is a disadvantage of fermenting ethanol
the land used to grow crops for fermentation could be used to produce food instead
what is biodiesel
made by chemically reacting fats and oils such as vegetable oil or animal fat with an alcohol producing fatty acid esters in a process called transesterification
what are the advantages of using biodiesel over diesel
- can be made from waste oil rather than using fossil fuel based oil
- carbon neutral (except for the energy required to produce and distribute it)
- some diesel vehicles can run on pure biodiesel but most on mixtures with regular diesel
- biodegradable
- contains virtually no sulfur so reduces SOx emissions
- produces less particulates, carbon monoxide and hydrocarbons than petrol than diesel
even though biodiesel produces less pollutants, what is the limitation
by the way in which nitrogen oxides are removed
what is the disadvantage of using biodiesel over diesel
produces more nitrogen oxides than conventional fossil fuels
give examples of biofuels
green diesel (derived from algae) and biogas (methane derived from animal manure and other digested organic material)
what does hydrogen produce when combusted
just water
2H₂(g) + O₂(g) —-> 2H₂O(g)
what are the advantages of using hydrogen as a fuel
- renewable, can be made by electrolysis of water
- can be stored and sent down pipelines (like methane)
- can be used in internal combustion engines or in a fuel cell to generate electricity
- produces no carbon dioxide, carbon monoxide or hydrocarbons when burnt
what are the disadvantages of using hydrogen as a fuel
- its production from water often depends on the use of electricity from fossil fuel power stations (though alternative energy sources for electricity are being developed)
- less energy dense than petrol (releases less energy)
- oxides of nitrogen are still produced at the high temperatures a hydrogen internal combustion engine runs at
which is more cheaper than transmitting electricity
if systems are costed over lifetime use in terms of money and energy then distributing hydrogen by pipeline would be cheaper. hydrogen would be used to store and distribute energy
what is being used to generate electricity in cars
fuel cells (on a small scale)hp
how are fuel cells being used to generate electricity
they convert chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidising agent in an electrochemical cell.
what is the fuel and product for fuel cells in cars
the fuel is oxygen and the product is water
what is the problem in designing cars run on hydrogen
a large volume of gaseous hydrogen is needed to get the mileage equal to a fuel tank of petrol.
what is one way to get cars to run on hydrogen
some way of storing hydrogen more compactly is needed
what is the solution for getting hydrogen as a fuel for cars
storing it as a liquid in a high pressure fuel tank
