Dissertations in Forestry and Natural Sciences

Taneli Väisänen: Effects of Thermally Extracted Wood Distillates on
the Characteristics of Wood-Plastic Composites
conversion and devolatilization take place; the maximum
temperature of the process typically ranges between 200 °C and
300 °C. (Williams and Besler 1996, Klass 1998, Nachenius et al.
2013)
Pyrolysis and charcoal production have a long history.
Traditionally, charcoal has been produced in kilns, but modern
charcoal production utilizes large retorts with capacities of
100 m 3 or even more. In addition, these systems are typically
combined with refining facilities to capture the volatile products.
The most common types of processes used in the industry are
the Reichert retort process, the SIFIC, and the Lambiotte process.
A Reichert facility typically consists of multiple retorts (up to
six), and therefore, has a high rate of production. For example,
the Reichert production facility operated by proFagus GmbH in
Bodenfelde, Germany, has been designed to produce
30 000 tons of charcoal, 5 200 tons of acetic acid, 1 800 tons of
pyroligneous spirit, and 12 000 tons of bio-oil per year. The
charcoal production capacity in a traditional Lambiotte retort is
12 000 tons per year. (Dahmen et al. 2010)
The decomposition of cellulose and hemicelluloses produces
primarily condensable vapors and non-condensable gases.
Lignin decomposes into liquids, gases, and charcoal. The
decomposition or volatilization of extractives produces liquid
or gas products. Minerals and ash remain solid in charcoal, and
they exert a catalytic effect on the pyrolysis reactions; these
compounds increase the yield of charcoal. (Williams and Besler
1996, Nachenius et al. 2013)
The pyrolytic production processes require only small
amounts of external energy. When the temperature is below
200 °C, the process is endothermic and it produces primarily
water, formic acid, and acetic acid. At 200–270 °C, the process
becomes partly exothermic. At this stage, the main products are
carbon dioxide, formic acid, and acetic acid. When the
temperature reaches 350–400 °C, the process reactions are
highly exothermic, producing a great number of products, such
as methanol, formaldehyde, and tar compounds. When 400 °C
is exceeded, the reaction heat becomes weakly endothermic,
66 Dissertations in Forestry and Natural Sciences No 222