Page 165 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

142 Biomass Gasification, Pyrolysis and Torrefaction

M f mass of feedstock (kg)
M w mass of water in feedstock (kg)
M ash mass of ash in feedstock (kg)
M g mass of diluted hot gas per unit mass of oil burnt (kg)
M oil mass flow rate of oil burnt (kg/s)
Py Pyrolysis number ( )
Q energy content (kJ)
theoretical heat load of dryer (kW)
Q d
Q 0 actual heat load of dryer (kW)
d
theoretical heat load of torrefier (kW)
Q t
Q 0 actual heat load of torrefier (kW)
t
heat loss from torrefier (kW)
Q tl
radius of biomass particle (m)
r p
2
S external surface area of a biomass particle (m )
temperature of gas at inlet of torrefier plant ( C)

T gi

ambient temperature of gas, ( C)
T 0
temperature of gas at exit of torrefier plant ( C)

T g0

torrefaction temperature ( C)
T t
space velocity of gas (m/s)
U g
U s space velocity of solids (m/s)
3
V volume of biomass particle (m )
W d dry biomass feed rate (kg/s)
W f feed rate of wet or as-received biomass (kg/s)
W g flow rate of diluted hot gas entering the torrefier (kg/s)
W t production rate of torrefied biomass (kg/s)
X d fractional heat loss from the drier ( )
Subscripts
ar as-received basis
bulk bulk
cooler cooling section of torrefaction plant
d dryer
daf dry ash free basis
db dry basis
feed feedstock or raw/wet/as-received biomass
pd predrying section
pdh postdrying heater
t torrefied product
tor torrefier
product value in product
Greek symbol
ρ density (kg/m )
3
λ thermal conductivity of biomass (kJ/C m)
η combustion efficiency of burner ( )