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FORMULARY
DISTILLATION
,1
||
=
|| || ||
,1 1
= + = + = 1−
,1
,1 ,1 ,1 ,1 ,1
+
,1
2
1
|| || || ||
1 1 1 2 1
= = γ α = / = −
+(1− )
1 , 1 1
−
1 1 1 2 1 2 1 10 1
α
|| || || ||
1
= − = = + = +
1+(α−1) +1
+ +1
1 1
1
− 1−φ
' −' '− 1
|| || || || ||
= = + φ = 1 − φ = =− +
' ' φ
− φ
( − )
|| || ||
,
φ = = φ λ + − λ = λ'
λ
−
|| || ||
= ( + )λ + [
] = λ + [ ] φ =
( − ) −
, || || || ||
+1
φ =− = (1 − φ ) = =
*
λ
−
+1
(1− )
1
||
= =
ψ α (1− )
1+ ( )
1−ψ
ABSORPTION
||
= =
||
→ ||
= γ () = = 1+ 1−
1
( )
||
=
|| ||
= − + = = −1
1+(1−) +(− )
( )
'− '
( ) → ||
' = = − ' +
'
−
( ) ( ) +1
−
||
λ ( − ) = − + − = =
+1
−
−1
STRIPPING
||
= =
||
→ ||
= γ () = = 1+ 1−
−
( )
|| || || ||
1
= = = = − =
1+(1−) +(− ) (1+ )− −
1
1 1
( )
− − +1
−
|| || ||
= = = = =
+1
−1 −
−1
−
( ) ( )
→
λ ( − ) = − + −
( )
( )
[ ] [ ] || ||
||
λ · ( − ) = · − = / = λ
5
( )
( )
||
= − = λ −
0
SIZING TRAY COLUMN
1. Guess for H (height between one tray and another). To do this you need:
a. define a vapor velocity referring to the entire section of the column A →
t
(reasonable values)
= 1 ÷ 2
b. calculate the total area
=
4
c. calculate the diameter
= π
d. calculate the height between one tray and the other (guess) = 0, 41
2. use the Fair diagram to give a value to the capacity factor K n,fl
ρ ρ
a. .
= =
ρ ρ
b. ρ −ρ
3. calculate the flooding speed through the column
= ρ
, , 1 2 3 4
assuming (as it depends on the geometry of the column which has not yet
= 1
2
been identified)
a. K is the correction factor linked to the surface tension:
1 0,2 0,2
( ) ( )
σ
[
/
] σ
[
/
] where σ is the surface tension. It is noted
= =
20 0,02
1
that for hydrocarbon systems the factor K =1 in fact these systems are the
1
reference.
b. K is the correction factor linked to the geometry of the plate (to the ratio
2
between the area of
the holes and the active area ):
ℎ
0,44
( )
i. if then
ℎ ℎ
< 0, 1 = 10
2
ii. if then
ℎ ≥ 0, 1 = 1
2
c. K is the correction factor linked to the size of the holes in the plate. The
3
flooding speed is reduced by 10% if the diameter of the holes is large:
i. if then → the flooding speed decreases u
> 6 = 0, 9 n,fl
ℎ 3
ii. if then
≤ 6 = 1
ℎ 3
d. K is the correction factor linked to any foam formation
4
4. calculate the net velocity assuming (arbitrary)
= = 0, 8
5 , 5
5. calculate the net area
=
6. calculate the total area . The area of
the downcomer depends on the
= +
length of the weir W.
a. A value of ( ) is decided
= ∼ 0, 7
b. from the following graph (A) we obtain the value of the ratio
c. calculate
=
1− 4
7. calculate the diameter and choose the largest nominal diameter closest to
= π
the value found
8. it is necessary to check the values
of K , K and H
2 5
( )
9. To check the value of ℎ
=
2
a. the active area is calculated: = − 2
2
i. the total area is recalculated using the nominal diameter
= π 4
ii. remembering the value of the graph, we calculate
= ·
b. The area of
the holes depends on the geometry of the holes. For example, for
2
( )
an equilateral triangular step the empirical formula ℎ
= · 0, 905 ·
ℎ
is valid where:
i. the value of must be fixed
ℎ
ii. A is the area in which the holes are present, which is equivalent to the
f
active area A of a fictitious circumference: = ' = ' − 2'
a
2
'
where and → b is the parameter to set
' = π ' = − 2
4
iii. to calculate refer to the curve of the graph (A)
'
1. The value is obtained
2. Knowing the diameter D it is possible to calculate .
= ·
3. It is assumed that = '
'
4. It is calculated ' '
5. The corresponding value is found in the curve
'
10.check the K value
5
a. the value of the flooding speed is recalculated:
ρ −ρ
= ρ
, , 1 2 3 4
b. the speed value is recalculated (since therefore
= ≠
A is different = −
n
c. the value of is recalculated to verify that it is
= 0, 4 < < 0, 8
5 5
,
11.it occurs that , therefore it is necessary to calculate the height of the liquid in
> 2ℎ
the downcomer ℎ = ℎ + ℎ + ℎ
( )
a. the height of the liquid h is calculated using the formula ℎ = ℎ + ℎ β
l
where 2
( )
3
i. the height above the weir is where L is the
ℎ = 0, 67 v
volumetric flow rate of liquid
ii. (correction factor since the height of the liquid can also contain the
height of the vapor entrained inside it) is calculated from the following
graph through knowledge of the “load factor” parameter = ρ
( )
ρ
1 1
where or, knowing ϕ,
= β = ( 1 + ϕ
) = 1+
2 2 ρ
b. the total height between two subsequent plates is calculated by
ℎ = ℎ + ℎ + ℎ
ℎ σ
i. h has just been calculated
l
ii. the pres
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