What is fuel blending exactly?

16 May 2019

Chemical engineers and engine designers are working hand in hand to produce new clean burning fuels to power the future.
Fuel blending has always been an art. Ordinary “petrol” has always been composed of a variety of organics obtained from the fractional distillation of raw petroleum, but with a variety of additives to improve its suitability for the internal combustion engine. The base product consists of lightweight hydrocarbons with between four and twelve carbon atoms, mostly alkanes (paraffins), alkenes (olefins), napthalenes (cycloalkanes) and traces of benzene.

Additive recipes improved the product in a variety of ways. Oxygen containing organics like ethanol, methyl tert-butyl and ethyl tert-butyl ether were (and still are) often added to improve the thoroughness of combustion, while the chief purpose of lead (before it was removed) was to retard that combustion to avoid engine knocking. Modifications were also needed to ensure cold weather starting. Detergents have been added to prevent deposits forming, while other chemicals act as preservatives.

For many years the composition purchased at roadside pumps remained fairly stable, and the regulation of racing sports quietened down innovation in that arena too. However, in recent years there have been a host of new motivations and technological opportunities to develop new fuels, and high-tech fuel developers are once again centre-stage.

Future proofing the industry

Leading motivations include the need to produce cleaner burning fuels to reduce urban air pollution, renewable fuels to reduce their carbon dioxide footprint, and fuels derived from agriculture in preparation for the eventually diminishing availability of fossil fuel sources.
However, fuels can never exist in isolation – their design is intimately linked to that of the engines in which they must be burned. Producing “drop-in” fuels that provide all these improvements in the billions of engines we already have without expensive or wasteful modifications is a particular challenge.

The good news is that fuels are now available in bulk from agricultural and chemical engineering sources that make improved fuels affordable at the pump and not just in the laboratory. Although we still need more refinery capacity to meet the eventual demand, blended fuels are already available at many petrol stations. Typically, diesels with 5-20% biodiesel (for example B5 and B20), or similar proportions of ethanol in petrol are suitable for use in the majority of current vehicles. Even cleaner and higher performance fuels, such as E85 (ethanol) and M85 (methanol), which were once only available on the race track, will gradually become common at our pumps as improved engine designs become the norm.
Flex fuel vehicles

An “FFV” is capable of running on a range of different fuels. Tax relief on cleaner fuels, and in many cases improved miles per gallon, help to offset the extra cost of their hybrid engines. Even if political unrest rations oil supplies, flex fuel vehicles will still be in the fast lane.
If fuel ever standardises on a single pure ingredient, it is a long way off. In the meantime fuel blending specialists will be in high demand.

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