Page 164 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory
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Chapter | 4 Torrefaction 141
W g 5 1.99 kg/s
W v 5 0.17 kg/s
W vl 5 0.119 kg/s
W 5 2:27 kg=s
0
g
Excess air coefficient, α 5 1 1 0.2 5 1.2.
W vl 0:119
Fraction of generated volatile, VL 5 0 5 5 0:052
0
fr
W 2:28
g
The parameters K and P are calculated as:
½ððA=FÞαÞC air T 0 1 LHVη 1 C oil T 0
K 5
W C g T g0 1 W vl LHV vl η
0
g
ð14:6 3 1:2 3 1:006 3 20 1 45500 3 0:95 1 1:7 3 20Þ
5 5 105:1
ð2:27 3 1:13 3 105 1 0:119 3 1286 3 0:95Þ
½ððA=FÞαÞ 1 1 ð14:6 3 1:2 1 1Þ
P 5 5 5 8:16
W 0 2:27
g
1 1:98 1:13 3 400
W oil 5 21 50:0077 kg=s
ð104:928:13Þ 2:27 1:13310510:0793128630:95
Equation (A.4) gives the fraction of flue gas recirculated back into the
torrefier:
ðW g 2 W oil :ðððA=FÞαÞ 1 1Þ ½1:99 2 0:0077ð14:6 3 1:2 1 1Þ
X 5 5 5 0:81
W 0 2:27
g
Percentage of gas recirculation 5 81%
SYMBOLS AND NOMENCLATURE
ASH ash fraction in raw or as-received biomass ( )
2
A r reactor cross-sectional area (m )
Bi Biot number (hV/λS)
C pd specific heat of dried biomass (kJ/kg C)
C pw specific heat of wet or as-received biomass (kJ/kg C)
C pg mean specific heat of flue gas (kJ/kg C)
3
EV energy density on volume basis (kJ/m )
EY energy yield ( )
HHV higher heating value on mass basis (kJ/kg)
h biomass particle to heating medium (gas) heat transfer coefficient (kJ/kg C)
heat utilization efficiency ( )
h u
21
K kinetic rate of torrefaction (s )
L latent heat of vaporization of water (kJ/kg)
LHV lower heating value on mass basis (kJ/kg)
MY mass yield ( )
M moisture fraction in raw or as-received biomass ( )
