Environmental Engineering Reference
In-Depth Information
moisture leaving in liquid form (no evaporation is assumed to take place). What is
the specific work input of the roller press (in kJ
kg
−1
dry fuel input)?
The c
p
of dry biomass is assumed to be constant at 1200 J
kg
−1
K
−1
, and the c
p
kg
−1
K
−1
.
of water is assumed to be constant at 4180 J
Solution
First, set up a macroscopic mass balance for the input biomass plug (stream 1),
where splitting of the dry biomass part and the moisture part starts:
φ
m
,
1
,
b
,
ar
=
φ
m
,
1
,
b
,
dry
+
φ
m
,
1
,
moist
M
ar
100
φ
m
,
1
,
moist
=
1
φ
m
,
1
,
b
,
dry
−
M
ar
with M
ar
being the wt% of moisture on an ar basis.
The mass balance over the dewatering press then becomes
=
M
ar
,
1
100
φ
m
,
1
,
b
,
dry
1+
φ
m
,
2
,
b
,
ar
+
φ
m
,
2
,
moist
−
M
ar
,
1
+
M
ar
,
2
100
=
φ
m
,
1
,
b
,
d
1+
φ
m
,
2
,
moist
−
M
ar
,
2
100
100−M
ar
,
1
−
100
100−M
ar
,
2
100 M
ar
,
1
−
M
ar
,
2
100
φ
m
,
1
,
b
,
d
φ
m
,
2
,
moist
=
φ
m
,
1
,
b
,
d
=
100
−
M
ar
,
1
−
M
ar
,
2
The energy balance for the roller press is
(
)
v
1
,
b
,
d
2
dE
cv
dt
=0=
Q
cv
−
W
cv
+
φ
m
,
1
,
b
,
d
h
1
,
b
+
+gz
1
,
b
,
d
(
)
v
1
,
moist
2
+
φ
m
,
1
,
moist
h
1
,
moist
+
+gz
1
,
b
,
d
(
!
+gz
2
,
b
)
v
2
,
b
2
−
φ
m
,
2
,
b
,
d
h
2
,
b
,
d
+
(
)
v
2
,
moist
2
−
φ
m
,
2
,
moist
h
2
,
moist
+
+gz
2
,
moist
Based on the assumptions, the kinetic and potential energy terms are not taken into
account as changes are negligible. Thus, with heat supply going to zero due to adi-
abatic compression for the power, we derive
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