swajames

I think you're right that it's the fractioning process that is probably the key here. As I understand it, the boiling point of the components that form petrol/gasoline is reached before that of the components that can comprise diesel fuels. It would seem logical that less energy would need to be applied to enable the extraction of the gasoline components compared to the higher temperatures that would need to be achieved to be able to reach the later fractions, including diesel. Thus, once you've extracted the gas component, part of what's left would or could be diesel (implying its the diesel that's the surplus, and that gasoline is an earlier fraction in contrast to ABC's suggestion a few posts back). Either way it does look like the low sulfur fuels are those that require more raw material to produce (there was an article in one of the papers here that made the same observation) and coupling that with the the lower boiling point of the gasoline components is where I was getting the support for the lower cost to produce and lower amount of raw material needed to manufacture a given unit of fuel. At the end of the day though I'm sure most of us here, and certainly me, are now getting out of our depth and supporting our arguments by deploying our Petrochemical Engineering degrees from the prestigious University of Google

aybeesea

Why would that be the case when (like for like) fuel economy (MPG;l/100km) is significantly improved when using diesel over using petrol?

Unless we know numbers, all else is emotive rhetoric.

ABC

Oh yes, I was entirely upside down (OK wrong!!) in my distillation fractions.

JWBMW

I thought the defractionating process was the same for most fuels with them drawing off the different grades/compounds at different levels in the tower i.e. the heavy diesel carbon chains are caught near the bottom and petrol drawn off further up the distillation stack. That way the crude is only processed once.

Oh yer I am a Civil Engineer and not a Chemical Engineer so my memory could be failing me.

pedrollo

Missed the point - or poorly explained.

For example:

For simplicity let's say that 10 gals of crude, among other things, produces 1 gal of petrol and 1 gal of derv.
A petrol car and a diesel car can therefore have a gallon each.

If both cars are diesel, to give each a gallon you would have to process 20 gals of crude (twice as much energy as processing 10), and throw away 2 gals of petrol.


Relative economy would have an effect of a few percent for sure but I was trying to make a bigger point.

ImolaRedM

Interesting story about diesel from the crapper

http://www.nzherald.co.nz/section/story.cf...jectID=10381404


Marlborough-based Aquaflow Bionomic yesterday announced it had produced its first sample of bio-diesel fuel from algae in sewage ponds.

It is believed to be the world's first commercial production of bio-diesel from "wild" algae outside the laboratory - and the company expects to be producing at the rate of at least one million litres of the fuel each year from Blenheim by April.