Develop a mass balance expression under different case scenarios and design a simple system to meet desired needs Objective Atoms are conserved but molecules may change to other forms...
Trang 1MASS BALANCE
Trang 2Conservation of Mass
Mass cannot be created nor destroyed.
Develop a mass balance expression under different case scenarios and design a simple system to meet desired needs
Objective
Atoms are conserved but molecules may change to other forms
Implication
Trang 3Types of Reactors
• Batch Reactors
• Completely Stirred Tank Reactors (CSTR)
• Plug-Flow Reactors
Q,
Cout
V V
to
t1
Trang 4• Dispersed Plug-Flow Reactors
• Packed bed Reactors • Fluidized Packed bed Reactors
Q,
Cin
Q,
Cout
Q, Cout
Q,
Cin
to
t1
Q
t2
Q
Trang 5Mass Balance- General Equation
Input
rate
Decay rate
Ouput rate
rate
Input,
Cin
System boundary
Decay
Cout
Completely-Mixed Tank Reactor (CSTR)
Trang 6Steady-State Conservative System
Steady state Accumulation = 0
Conservative Decay = 0 Input rate = Ouput rate
Stream
Qs, Cs
Mixture
Qm, Cm Waste
Qw, Cw
CSTR
Input
rate = QsCs+QwCw
Ouput
rate = Qm
Cm
m
w w s
s m
Q
Q C Q
C
}
Trang 7Steady-State with Nononservative Pollutants
Steady state Accumulation = 0
Nonconservative Decay rate (1st-order) = kCV = kCmV
Input
rate = QsCs+QwCw
Decay
rate = kCm
V
Stream
Qs, Cs
Mixture
Qm, Cm Waste
Qw, Cw
CSTR
V k Ouput
rate = Qm
Cm
Input
rate
Ouput rate
rate +
kV Q
Q C Q
C C
m
w w s
s m
+ +
=
Trang 8Reaction Term
Trang 9Example
kV Q
Q C Q
C
C
m
w w s
s m
+
+
=
Stream
Q s =5 m 3 /s
C s =10 mg/L Outgoing
Q m =?
C m =?
Waste
Q w 0.5 m 3 /s
C w =100mg/L
Well-mixed lake V=10x106 m3
k=0.2/day
Solution
L
mg 5
3 ) m 10 10
)(
s 60 60
24
day day
1 2 0 (
) s
m 5 5
(
) s
m 5 0
)(
L
mg 100 (
) s
m 5
)(
L
mg 10
( C
3 6 3
3 3
×
×
×
× +
+
=
Trang 10Example
kV Q
Q C Q
C C
m
w w s
s m
+
+
=
Solution
Stream
Q s =5 m 3 /s
m2 =?
Waste
Q w 0.5 m 3 /s
C w =100mg/L
C m1
Q
C C
m
m 1
m 2
m
+
=