Page 254 - Biosystems Engineering

232 Cha pte r Se v e n

(acids, aldehydes) and water (families A and B) and oligomers (families
E and F). Furans and phenols, sugars, diphenols, and some extractive-
derived compounds (families C and D) contribute more positively to
the fuel properties of bio-oils (Garcia-Pérez et al. 2007a, 2007b, 2008).
A handicap facing both the crude bio-oil producers and manufac-
turers of boilers, gas turbines, and diesel engines is the lack of classi-
fication and specification for crude bio-oils. To label an organic liquid
as a fuel, it must fulfill a set of requirements in relation to combus-
tion, storage, handling, and safety (to the engine and its environment)
(Moses 1994; Diebold et al. 1999; Oasmaa and Czernik 1999). The IEA
Pyrolysis Activity Group proposed a bio-oil classification strategy
similar to the one used for petroleum fuels (Oasmaa and Czernik
1999). Consequently, bio-oils were classified as light bio-oils (viscos-
ity similar to ASTM No. 2), light medium bio-oils (viscosity similar to
ASTM No. 4), medium bio-oils (viscosity similar to PORL 100), and
heavy bio-oil (viscosity similar to fuel No. 6). This classification has
been poorly applied but remains as a reference of how the bio-oils
could be classified.
Combustion of Crude Bio-Oils
Bio-oil combustion tests has been ongoing ever since the development
of biomass pyrolysis technologies. Many combustion tests at atmo-
spheric pressure in flame tunnels and boilers have been performed in
several laboratories: Massachusetts Institute of Technology (Shihadeh
et al. 1994), Canada Centre for Mineral and Energy Technology
(Banks et al. 1992; Lee 1993), Ente Nazionale per l’Energia Elettrica
(Rossi et al. 1993; Barbueci et al. 1995), Coordination Geoinformation
Services (Salvi and Salvi Jr. 1991), Red Arrow Products Co. (Freel et al.
1990; Freel and Huffman 1994), Neste Oil (Gust 1994, 1997), VTT Energy
(Oasmaa et al. 2001), Monash University (Stamatov et al. 2006), and
International Flame Research Foundation (IFRF) (van de Kamp and
Smart 1991, 1993).
An advantage of converting biomass into liquid fuels is the pos-
sibility of using these fuels in highly efficient engines to produce elec-
tricity. Gas turbines and diesel engines offer higher thermal efficien-
cies than the Rankine cycles (efficiency of around 26 percent) (Roy and
Morin 1998). These higher efficiencies have been the main driving
force for testing crude bio-oil in engines since the 1990s (Kasper et al.
1983; Solantausta et al. 1993, 1994; Shihadeh et al. 1994, Gros 1995; Jay
et al. 1995; Andrews et al. 1996, 1997; Suppes et al. 1996; Leech 1997;
Frigo et al. 1998; Bertoli et al. 2000; Lopez-Juste and Salvá Morfot 2000;
Ormrod and Webster 2000; Shihadeh and Hochgreb 2000; Strenziok
et al. 2001; Chiararamonti et al. 2003). An excellent review on bio-oil
combustion tests in gas turbines and diesel engines can be found else-
where (Czernik and Bridgwater 2004; Chiaramonti et al. 2007).
Nevertheless, some problems in the use of crude bio-oil in diesel
engines and gas turbines still remain unsolved. Although boilers can