Alan G. Rhodes gave a technical presentation, on the above topic, at the
Danish Canadian Club.
Attendance was high. (Some 30 + attendees)
The chief reasons for upgrading heavy oil are:
Transportation problems.
Marketing problems.
The transportation problem is that heavy oil is too viscous to flow through
the pipeline system without the use of diluent to reduce the viscosity.
The marketing problem is that even if we are able to transport heavy oil,
the content of commercially interesting fractions is so low that:
It is of interest only to asphalt producers.
It is of interest to a refinery which can convert the heavy oil to valuable
products. The cost of this will be reflected in the price paid for heavy
oil.
To upgrade heavy oil to something approaching conventional oil, one can
either:
Reject carbon.
Add hydrogen.
In practice a combination of both approaches is used.
The primary conversion process is either:
Coking (carbon rejection) by delayed or fluid coking
Addition of hydrogen via LC fining or H-Oil
The products from either of the above processes are somewhat unstable and
could form gums etc. To overcome this, secondary upgrading is employed. Universally
this is done by addition of extra hydrogen.
Whilst stabilising the products the opportunity is taken to reduce the sulphur
and nitrogen content of the synthetic crude oil.
The results of upgrading are a synthetic crude oil which has:-
Low sulphur and nitrogen content.
No residuals.
However, despite the above desirable properties, in a competitive market
situation, the following disadvantages should be noted:-
Relatively poor cetane and smoke point values i.e. poor diesel and jet
fuels.
Poor characteristics of the heavy gas oil fraction (cat cracker feed).
To remedy these disadvantages, still more hydrogen must be added.
The challenge for the next millennium is to produce an acceptable synthetic
crude oil economically.
