Potentiale zur energetischen Nutzung von Biomasse in der ... - EPFL

Anhang 29
Bundesamt für Energie BFE
Production of Fischer-Tropsch liquids from biomass feedstock
Current developments in Fischer-Tropsch technology focus on producing clean hydrocarbon fuels
based on biomass feedstock. Fischer-Tropsch liquids can be produced from different types of
lignocellulosic material. Another option is to feed the conversion process with bio-oil, e.g. pyrolysis oil.
Additional components that would be required for the use of biomass feedstock include the biomass
pre-treatment unit and the syngas cleaning and conditioning unit. The basic steps of producing FT
liquids from biomass combined with heat and power generation are depicted in Figure 1. For the
production of one ton of Fischer-Tropsch diesel about 8.5 tons of wood are needed. The yield of
liquid fuels is thus about 150 litres per ton of wood 4 (Boerrigter and Den Uil, 2002).
Biomass
Pre-treatment
and
gasification
Gas cleaning
and
conditioning
GT combined
cycle/HRSG/
steam turbine
FT
synthesis
reactor
Product
recovery and
upgrading
Figure 1 Basic components of the biomass based FT-liquids/CHP plant (Hamelinck et al., 2003).
Electri
city
FTliquids
The use of biomass as an input for Fischer-Tropsch processes is still in the development phase. The
integration of biomass gasification and Fischer-Tropsch synthesis has not yet been demonstrated on
commercial scale. Current research and development activities are focused on cleaning and
conditioning of synthesis gas, development of several types of catalysts, reducing the amount of inert
components in the feed gas, and the utilisation of by-products. The production of Fischer-Tropsch
liquids in combination with electricity and heat seems to be the most economically efficient option.
Economical analysis of Fischer-Tropsch process using biomass
feedstock
To date one of the most comprehensive studies on the production cost of liquid bio-fuels via the
Fischer-Tropsch process was carried out by Hamelink et al. (2003). Different configurations of
equipment components were compared to reflect anticipated efficiency improvements which reside
mainly in combined production of FT liquids with electricity, application of pressurised gasifiers, and in
combining high selectivity with high conversion in the FT reactor. A typical cost breakdown is given in
Table 1 on the example of a 400 MW th input plant (or 168 MW FT,HHV output) applying conventional
technologies. Such a plant could be expected to be operational in 2010. It consists of a 25 bar oxygen
fired gasifier, followed by a tar cracker and wet gas cleaning, and a solid bed FT reactor with 70%
4 3
If 1 ton of wood is gasified, this results in 2 mn of bio-syngas. From this gas, 175 litres of Fischer-Tropsch
wax (long-chain hydrocarbons) can be produced, which is converted to 150 litres of FT diesel by means of a
cracking process (Boerrigter and Den Uil, 2002).
Heat