Processing of Primary Fischer-Tropsch Products - University of Alberta

The art of HTFT refining lays not so much in meeting the fuel
specifications as in exploiting the unique feed advantages offered by the FT
product. In conclusion it can be said that a HTFT product lends itself to an
integrated fuels and chemicals refining approach. Refining with the aim to
produce only fuels or only chemicals can be done, but this would be sub-optimal.
6. UPGRADING OF LOW TEMPERATURE FISCHER-TROPSCH
PRODUCTS
6.1 Characterisation of the primary LTFT products
The typical LTFT plant would produce two primary products: a light
fraction, usually liquid at room temperature, and a heavy fraction, usually solid
at the same conditions. The former is often named hydrocarbon condensate or
simply condensate and includes hydrocarbon species with a final boiling point
around 370~ The latter, also known as wax, includes the heavy paraffins.
There are two other product streams: (i) light hydrocarbons gases, mostly
generated during the FT synthesis, and (ii) reaction water, which include some
dissolved oxygenates like alcohols and organic acids. The gas stream can have
many applications as a fuel gas. The reaction water needs to be further processed
and, at some locations, might even become a valuable product. There are several
options for the purification of LTFT reaction water [59].
The primary LTFT products have been described in detail in Chapter 3 and
in the literature [60]. Typical distillation ranges for the LTFT Condensate and
Wax are presented in Table 4.
While the main species in the LTFT primary products are linear paraffins,
smaller contents of olefins and oxygenates are present as well as some branched
paraffins. The product slate for a particular system depends on the reactor
configuration used, operating conditions and the catalyst that is employed [61].
FT Wax production is about double of that of the FT Condensate.
Table 4
Typical distillation range for LTFT syncrude fractions
FT Condensate
Distillation Range % vol
C5-160~ 44 3
160-270~ 43 4
270-370~ 13 25
370-500~ - 40
>500~ - 28
FT Wax
% vol
The composition and yield immediately suggest that an effective approach
to the refining of the LTFT primary products should include some form of
hydroprocessing. The recovery of the oxygenated hydrocarbons is always an
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