Biomedical Engineering Reference
In-Depth Information
O
fractional of oxygen in the fuel in dry basis (
)
amount of char produced per N m
3
of product gas (kg/N m
3
)
P
c
q
c
heating value of char (kJ/kg)
Q
power output of the gasifier (MW
th
)
external heat addition to the system (kJ/N m
3
)
Q
ext
lower heating value of the product gas from gasification (MJ/N m
3
)
Q
g
Q
gasification
heat supplied to gasify 1 mol of biomass (kJ/mol)
heat loss from the gasifier (kJ/N m
3
)
Q
loss
r
steam gasification reaction rate (kg/s)
R
universal gas constant (0.008314 kJ/mol K)
S
fractional of sulfur in the fuel in dry basis (
)
steam-to-carbon molar ratio (
)
SC
t
time (s)
T
temperature (K)
T
f
gas temperature at the exit (
C)
T
g
gas temperature (
C)
T
0
gas temperature at the entrance (
C)
U
g
fluidizing velocity (m/s)
volume of the fluidized bed (m
3
)
V
volume of the bed (m
3
)
V
bed
V
daf
volatile based on dry-mass-free basis
gas generation rate (m
3
/s)
V
g
volumetric flow rate of product gas (N m
3
/s)
V
g
V
i
volumetric fraction of gas species i (
)
W
total steam needed in
Eq. (8.22)
(kg/s)
W
in
rate of the char moving in (kg/s)
W
out
rate of the char moving out (kg/s)
x
char
weight of the reacting char (kg)
X
fraction of char in the feed converted (
)
X
c
fixed carbon fraction in the fuel (kg carbon/kg dry fuel)
X
char
char fraction in bed (
)
X
g
fraction of steam used up in gasification
ε
voidage of the bed (
)
λ
I
Lagrangian multiplier for species i (
)
density of air at the opening temperature and pressure of the gasifier (kg/m
3
)
ρ
g
θ
residence time of char in bed or reactor (s)
bed density (kg/m
3
)
ρ
b
density of bed solids (kg/m
3
)
ρ
s
η
gef
gasifier efficiency (
)
η
ceff
cold-gas efficiency (
)
η
cg
cold-gas efficiency of the gasifier (
)
η
hot-gas efficiency of the gasifier (
)
hg
η
net gasification efficiency of the gasifier (
)
net
Δ
H
T
heat of formation at temperature T (kJ/mol)
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