Carbon, sulphur and hydrogen in oil refineries

Accurately calculating the global carbon balance in oil refinery and petroleum product end-use systems is a challenge of nightmare proportions. All except the lightest of the output streams are of uncertain and variable chemical composition.

Oil refining deals with potentially millions of different chemical compounds all mixed up together. Matters are not too difficult up to the six carbons level, the light gasoline region. Beyond six, the number of possible combinations of carbon (linked by single and double bonds in rings and chains) and hydrogen increases exponentially. Then there are the myriad varieties of sulphur and nitrogen compounds commonly present in crude oils. The measurement and tracking of individual compounds through the refining processes, ‘refining with tweezers’ as it is jokingly called, is clearly impossible.

To cap the complexities, where properties of complex pure hydrocarbon compounds have been measured, published data do not always all run in neatly predictable progressions.