Page 145 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

122 Biomass Gasification, Pyrolysis and Torrefaction

between torrefied pellet and raw wood pellet, we take this value to be
3
650 kg/m . So, the volumetric density of energy of torrefied pellet, EV p,t ,
would be
3
EV p;t 5 HHV t 3 ρ 5 24:59 3 650 MJ=m 5 15:98 GJ=m 3
p
Raw Torrefied Wood Torrefied
Wood Wood Pellet Pellet
Volume energy density, MJ/m 3 3876 4512 8398 15,983
Mass energy density (as-received 12.92 24.59 19.28 24.59
basis), MJ/kg

c. Increase in energy density:
The volumetric energy density of raw wood was based on initial
value 5 (15,983 3876)/3876 5 3.12.
There is thus an increase of 312% of volumetric energy density of
biomass after torrefaction.
The increase in volumetric energy density due to pelletization
alone 5 (12,530 3876)/3876 5 2.23 or 223%.

4.7 TORREFACTION TECHNOLOGIES
A typical torrefaction plant would include several units like biomass han-
dling, preparation, dryer, torrefier, and product cooler. Among these, the tor-
refaction reactor is most important. Presently, vendors are offering many
designs of torrefier. This section presents a broad overview of those designs
of torrefier by classifying them under specific groups. Table 4.9 presents a

TABLE 4.9 Torrefaction Reactor Technologies Supplied by Different
Developers
Torrefier Technology Technology Supplier

Rotary drum reactor CDS(UK), Torr-coal (NL), BIO3D(FR), EBES AG(AT), 4Energy
Invest (BE), BioEndev/EPTS (SWE), Atmosclear S.A. (CH)
Screw conveyor BTG (NL), Biolake (NL),FoxCoal (NL), Agri-tech (US)
Multiple hearth CMI-NESA (BE), Wyssmont (US)
Entrained Topell (NL), Airex (Canada)
Fluidized Topell (NL)
Mircowave Rorowave (UK)
Source: Updated from Kleinschmidt (www.kema.com).