Scale-up and Demonstration of Fischer-Tropsch Technology

6 D. Schanke et al.
To date, more than 100 tonnes of catalyst have been produced for use in the semicommercial
demo plant. The scale of production (up to 1 ton/d) ensures minimal scaleup
risk for the catalyst manufacturing plant for a commercial project.
5. Performance of the demonstration plant
5.1. Catalytic performance
During the catalyst manufacturing campaigns, an extensive program of quality control
was carried out, using a pilot plant and other catalyst test reactors. After developing and
optimising the catalyst manufacturing procedures, the activity and selectivity of catalyst
produced at large scale does not differ from catalyst produced in the laboratory.
Furthermore, it was found that the catalyst activity and selectivity in the semicommercial
demo plant was similar to what is usually observed in the pilot plant.
Table 2. Example demo plant performance
Feed gas composition
H2
CO
CO2+CH4+N2
58 mol %
27 mol %
Balance
Reactor pressure 1600 kPa
Reactor temperature 232 o C
Gas hourly space velocity 3950 Nm 3 /toncatalyst/h
Conversion per pass
H2
CO
66 %
67 %
5.2. Wax separation
Predictably, the separation of wax from the slurry has been the most challenging aspect
of the technology development. After very good results in smaller scale pilot reactors,
the first trials in the semi-commercial demo plant gave low wax separation performance
after some time of operation and higher than expected levels of catalyst fines in the wax
product.
After several modifications to the wax separation system as well as the introduction of a
2 nd generation FT catalyst, the plant was able to be operated at sustainable, high wax
separation rates with minimal catalyst fines in the wax product (see fig. 4). The
performance of the wax separation system is known to be strongly dependent on the
particle size distribution of the catalyst in the reactor slurry. It became apparent that the
attrition characteristics of the catalyst are a function of the scale of operation, the
operating conditions as well as the properties of the catalyst (Wagner, 2008). This is