lecture 6: separation process design, sizing & selection
TRANSCRIPT
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 1
Lecture 6: Separation process design, sizing & selection
Chapters 4, 7 (Textbook) plus additional material*
• Part-1: Introduction
• Part-II: Two-phase (equilibrium) separations
• Part-III: Separation of azeotropic mixtures
• Part-IV: Other separation processes
• See also ”Separation Process Principles” by Henley, Seader & Roper
Chapters 7, 11 & 13 of book for distillation & absorption, and
chapter 14 for membrane based separation
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 2
Downstream Separations: The main issues
• When is separation necessary?
• What are the mechansims of separation?
• Which mechanisms and how many need to employed to
achieve a desired separation?
• How to configure/select/design the separation tasks?
• How to verify if the desired separation can be achieved?
This lecture will provide a quick overview of the above topics – more
details can be found in courses on separation process principles
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 3
When is separation necessary?
…Crude
separation
processes
Oil productsCrude Oil
Separating
different oil
products from
crude oil
Reactor
N2
H2
NH3
Argon
Methane
N2, Argon
H2, Methane
Recovery &
purification of
chemicals
(products)
Two Examples
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 4
Downstream Separation in Chemical Process Design - I
Extraction Recovery Purification Finishing
Chemical processes without reaction
• Crude oil based refinery for gasoline, and other fuel products
• Seeds and other biomass based edible oil extraction processes
• Herbs, plants based extraction of specialty chemicals
• ...........
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 5
Downstream Separation in Chemical Process Design - II
Reactor Separation
EL, Pl, M
W
EL, Pl, M recycle
EL, Pl, M
EA
DEE
Waste
Water recycle
Identify and design the sequence of separation tasks that need to be performed
in order to recover and purify the products, recycle the reactants and purge the
inerts that enter the process
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 6
Phase
Creation
Feed
Phase 1
Phase 2
Feed
Force field
or gradient
Phase 1
Phase 2
(a) (c)
Barrier
Feed
Phase 1
Phase 2
(e)
Feed
Phase 1
Phase 2(d)
Feed
Phase 1
Phase 2MSA
(Solvent)
(b)
Which mechanisms of separation?
a) Phase Creation (eg, distillation); b) Agent-based separation (eg,
extraction); c) Barrier (eg, pervaporation; filtration); d) Solid agent
(eg, adsorption); e) Force field or Gradient (eg, ion-exchange;
centrifuge)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 7
• Analyze mixture to be separated (collect data or predict behaviour)
• Identify relation between mechanism and system property (separation
principles)
• Generate and test alternatives (select, design, verify)
How many mechanisms and which mechanisms?
A, B, C, D, E, F
A, E, F / C, D, B
C / D, BA, F / F
A / B, C, D, E, F
• Depends on how many
chemicals need to be
separated (NS)?
• Minimum number of
separation tasks is NS-1
•For each separation task,
find the appropriate
separation mechanism
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 8
How to configure separation tasks? - Distillation Trains
• Order the driving force diagrams in terms of fij| max = abs(yi – xi); • Configure the distillation train in terms of fij| max (easiest separation first –
largest driving force equivalent to minimum energy);• Design each distillation column such that it uses the maximum driving
force (note: only 4 separation tasks A-B; B-C; C-D; D-E)
Secondary Separation Efficiencies at P=1 atm.
0
0.05
0.1
0.15
0.2
0.25
0.3
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Liquid composition, mole fractions of the lightest compounds
SS
E
Propane iButane
iButane nButane
iPentane nButane
nPentane iPentane
B
C
D
E
A
A
B
C
D
E
Separation of propane (A), i-butane (B), butane (C), i-pentane (D),
pentane (E)
A/B
C/D
B/C
D/E
9
How to configure separation tasks? – Extraction plus recovery
Main Features:
• Extraction (2-liquid
phases); use of
solvents
• Recovery of solvents
& solute (requires
energy for VL
separation)
• Other forms of
extraction could be
membrane-based, ion-
exchange, etc., that
does not require the
recovery step)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 10
Part-II: Two-phase (equilibrium)
separations: Design issues
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 11
2-phase VLE based separation: design degrees of freedom?
Typical 2-Phase VLE-Model
Equilibrium relation xi gi jisat Pi
sat = yi jiVP i = 1,2,….c
Condition Si xi = Si yi = Si zi = 1
Mass Balance Z zi = V yi + L xi i = 1,2,….c
Feed, Z
Vapor, V
Liquid, L
T, P
Degree of Freedom Analysis F = c - p +2
For p = 2, F = c. There are 2c+3 Equations and 3c + 5variables (not counting gi , ji , Pi
sat ). Therefore, c + 2variables need to be specified. For example, specify Z, T, P
and (c-1) z compositions.
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 12
Some Definitions
Equilibrium Constant (VLE) Ki = yi/xi
•Ideal System Ki = Pisat (T) / P
•Non-ideal Liquid & Vapor Ki = gi jisat Pi
sat /( jiVP)
•Non-ideal Liquid, ideal vapor Ki = gi Pisat /P
•Any P & T Ki = jiL / ji
V
Relative volatility ij = yj xi / (xj yj) = Pisat/Pj
sat
Rewriting in terms of yi yi = xi ij/[1+ xi(ij - 1)]
Driving Force Dij = yi - xi
Rewriting in terms of yi Dij = xi ij/[1+ xi(ij - 1)] - xi
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 13
Binary systems with different volatility
Liquid composition, xi
0.0 0.2 0.4 0.6 0.8 1.0
Drivin
g F
orc
e,
FD
i
0.00
0.05
0.10
0.15
0.20
0.25
0.30Distillation, 1 atm.
Distillation, 5 atm.
Pervaporation
Extractive distillation
XY-(PT) phase diagram (in
terms of relative volatility)
DX-(PT) phase diagram (in
terms of driving force) – shown
for different separation types)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 14
VLE based separation: Model w.r.t. ij or Dij
Typical 2-Phase VLE-Model
Equilibrium condition yi = xi ij/[xi (ij - 1) + 1] w.r.t. relative volatility
or (eq.1) Dij = xi ij /[xi (ij - 1) + 1] - xi w.r.t. driving force
Mass Balance Z zi = V yi + L xi i = 1,2,….c
or yi = (R + 1) zi – R xi where R = L/V
or (eq. 3) Dij = (R + 1) (zi –xi)
Feed, Z
Vapor, V
Liquid, L
T, P
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 15
Dij = yi - xi = xi ij / (1 + xi (ij - 1)) - xi
Dij = (R+1)(zi – xi)
Graphical calculation technique for V-L based separation
When Dij = 0, there is no separation and zi = xi
When xi = 0 or L= 0; R= L/V= 0 & Dij = yi - xi = zi (everything is vaporized)
When R = specified; xi = Dij /(R + 1) + zi (point of intersection of Eqs. 1 & 3)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 16
Visualization of 2-phase separations: P-XY & T-XY diagrams
L
VV & L
x1 and y1
Bubble point
Dew point
A C
B
x1 and y1
L
V
V & L
P-xy diagram at constant T T-xy diagram at constant P
A
C B
For a feed at C, L/V = CB/AC; at constant T, if you compress a vapor you
get a liquid and vice versa. At constant P if you heat a liquid you get a
vapor and vice versa. If you have a feed mixture in the 2-phase (V&L)
region, it will split into a liquid and a vapor
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 17
VLE - Binary Systems: Azeotropic systems
Ethanol - Water Methanol - Toluene
XY-PT phase diagrams. At the azeotrope, xi= yi,
therefore, Ki=1 and/or ij = 1. Separation beyond the
azeotropic point is not possible
x1
y1y1
x1
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 18
Visualization of 2-phase separations: azeotrope systems
Methanol-Toluene T-xy & P-xy diagrams
Generate these diagrams as a function of P to see if the location of the azeotrope can be moved
x1, y1
TP
x1, y1
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 19
Types of VLE-phase separation models & solution approaches
Problem Specification
Isothermal flash (T, P, F, z)
*Bubble-point T (P, x)
*Dew-point T (P, y)
*Bubble-point P (T, x)
*Dew-point P (T, y)
Adiabatic flash (Q=0, P, F, z)
Non-adiabatic flash (Q, P, F, z)
% Vaporization (V/F, P)
* Note: Degrees of freedom = c + 1
Isothermal flash: fast solution
Specified: F, z1, z2, ..zc-1, T, P
Solve for = V/F with fixed Ki
1. Calculate Ki = Pisat(T)/P
2. f = Si zi(1-Ki)/[1+ (Ki-1)] = 0
3. V = F ; L = F - V
4. xi = zi / [1+ (Ki-1)]
5. yi = ziKi / [1+ (Ki-1)] = xi Ki
6. Q = hV V + hL L – hF F
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 20
Separation of Binary Mixtures by Distillation: review
1
NF
NP
Feed
F, zF
Distillate, D, xD
Bottom product, B, xB
Condenser
Reboiler
Recycle, L0
Vapor boilup VNP+1
V1
V2
VNF
VNP
VNF+1
L1
LNF-1
LNF
LNP-1
Component Mass Balance
Overall
F zF = D xD + B xB
Rectifying section
yn+1= Ln/Vn+1 xn + D/Vn+1xD
y = [R/(R+1)] x + [1/(R+1)]xD
Stripping section
ym+1= Lm/Vm+1 xm - B/Vm+1xB
y = [(VB+1)/VB] x - 1/(VB+1)]xB
Equilibrium relation
yi = xi ij / (1 + xi (ij - 1))
QC
QR
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 21
•Component Mass Balance
•Overall
•F zF = D xD + B xB
•Rectifying section
•yn+1= Ln/Vn+1 xn + D/Vn+1xD
•y = [R/(R+1)] x + [1/(R+1)]xD
•Stripping section
•ym+1= Lm/Vm+1 xm - B/Vm+1xB
•y = [(VB+1)/VB] x - 1/(VB+1)]xB
•Equilibrium relation
•yi = xi ij / (1 + xi (ij - 1))
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 22
Driving force based design - I
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0.0
0.1
0.2
0.3
0.4
FX
FX'
Pinch point
Slope correponding
to RR > RRmin
Slope correponding
to RRmin
BA
D'
DY
DX
D
Dri
vin
g F
orc
e, F
Di
Light compound composition, xi
•Given a mixture to be separated into two products in a distillation column with N trays. What is the optimal (with respect to the costs of operation) feed plate location and the corresponding reflux ratio for
different product purity specifications ?
II
I
B
A
NF
A
B
Dx
I
II
D D’ NF = N(1-D
x)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 23
Relation between ij, Dij(max), Xi (max)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0 2 4 6 8 10 12
Alfa (Constant)
Xi M
ax
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Max F
Di
Xi Max
Max FDi
24
Identification of design targets
25
Simple and fast reverse design method
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 26
Problem Solution
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 27
Driving force based design - II
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 28
Part-III: Separation of azeotropic mixtures
(chapter X of textbook, see also chapter 11 of
Seader & Henley book)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 29
Separation of an azeotropic mixture
• Mixture analysis
Identification of an azeotrope.
• Possible separation techniques
Pressure swing.
Extractive/azeotropic distillation.
• Solvent identification and validation
• Flowsheet configuration
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 30
Binary Azeotrope:A binary azeotrope is when a 2 component, 2 phase system of gas and liquid in
chemical equilibrium has the same composition in both phases.
Gas phase, composition: ya, y
b
Liquid phase, composition: xa, x
b
Azeotropic condition:
xa = ya, xb = yb
Mixture analysis
Whenever you have the problem of separating a mixture, a good starting
point is always to do a mixture anaysis.
This can include both pure component and mixture properties.
The mixture analysis will imediately give information both intuitively
and to a computer aided system on what kind of separation is possible.
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 31
Identification of an azeotrope
Azeotropes is found by VLE (Vapor-Liquid Equilibria) mixture
analysis.
This can be either database lookup for VLE datapoints or the
datapoints can be calculated with a thermodynamic model.
0 1
0
1
x
y
Comp A
Comp A
By the definition of an azeo-
trope, in a x-y plot the curve
crosses the diagonal, at the
azeotrope composition.
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 32
Possible separation techniques
Conventional distillation not possible, if 2 pure products are desired.
Possible solutions to this problem:
• Use separation techniques which are not exploiting
differences in vapor vs. liquid phases, i.e. membranes or liquid-
liquid extraction.
• Pressure swing.
• Extractive / azeotropic distillation.
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 33
Acetone - chloroform
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
VLE-PhaseDiagram: Pres.= 1.00 atm
CHCl3 mole % ACETONE
CH
Cl3
m
ole
% A
CETO
NE
ACETONE
CHCl3
Azeotrope ~ 38 mole% acetone, 64.5 °C, maximum boiling
50
52
54
56
58
60
62
64
0 20 40 60 80 100
VLE-PhaseDiagram: Pres.= 1.00 atm
Tem
pera
ture
(°C
)
ACETONE CHCl3
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 34
Pressure swing
0
20
40
60
80
100
0 20 40 60 80 100
VLE-PhaseDiagram: Pres.= 1.00 atm
METHANOL mole % CH3-ACETA TE
ME
TH
AN
OL
m
ole
% C
H3-A
CE
TA
TE
CH3-ACETATE
METHANOL
0
20
40
60
80
100
0 20 40 60 80 100
VLE-PhaseDiagram: Pres.= 6.00 atm
METHANOL mole % CH3-ACETATE
ME
TH
AN
OL m
ole
%
C
H3-A
CE
TA
TE
CH3-ACETATE
METHANOL
Pressure swing distillation is exploiting the fact that for
some azeotropes the composition changes with pressure
System: methanol – methyl acetate
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 35
Extractive distillation
The addition of a third component (solvent/entrainer) to the
binary system in order to facilitate the separation by distillation.
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
Vapour
Diagonal
Vapour 60.0
VLE-PhaseDiagram: Pres.= 1.00 atm
CHCl3 mole % ACETONE
CH
Cl3
mole
%
A
CE
TO
NE
solvent mole %
ACETONE
CHCl3
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 36
Hybrid Separation: Driving force
Separation by single distillation operation not feasible; hybrid separation schemes (solvent based extraction or
distillation plus pervaporation or pressure swing distillation) feasible
Secondary Separation Efficiency, Methanol MTBE
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Liquid Composition, Mole Fraction Methanol
AB
S(y
i-x
i)
Distillation
column 1
Pervapo-
ration
Column 1 at P1Column 2 at P2
Solvent based
separation
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 37
Solvent identification (I)
The computer tool must be able to solve the following problem:
Given: A set of desired properties (pure and mixture)
Needed: Description of compounds with these properties
The solvent can be found in a solvent database or by the use
of a computer tool.
Computer Aided Molecular Design (CAMD) programs can solve
this.
General functionality:
1. Combine molecular fragments to describe complete molecules
2. Predict the properties of the molecular descriptions
3. Reject descriptions with undesired properties
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 38
Solvent identification (II)
Desired properties for the entrainer:
1. If it is a minimum boiling azeotrope the boiling point of
the entrainer should be lower than the azeotropic
temperature and vice versa.
2. The boiling point should not be to high in order to have
small energy consumption.
3. Should not be harmful to the environment.
4. Should not form azeotropes with any of the two
compounds.
5. High selectivety:
6. Low solvent loss:
7. ...
SiS
jS
s
g
g
sJ
sv.L
1S
g
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 39
Solvent validation (I): Identify distillation boundaries
0.0
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.6
0.7
0.7
0.8
0.8
0.9
0.9
1.0
1.0
1-PROPANAL
METHYL-ACETATE METHANOL
( 338.0 K)
( 321.5 K)
( 331.0 K)
328.1 K
Azeotrope
Distillation boundary
Residue curve
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 40
Solvent validation (II): Separation feasibility
0.0
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.6
0.7
0.7
0.8
0.8
0.9
0.9
1.0
1.0
1-PROPANAL
METHYL-ACETATE METHANOL
( 338.0 K)
( 321.5 K)
( 331.0 K)
328.1 K
Azeotrope
Feed 1
D1, Feed 2
B1
D2
B2
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 41
Solvent validation (III): Flowsheet configuration
0.0
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.6
0.7
0.7
0.8
0.8
0.9
0.9
1.0
1.0
1-PROPANAL
METHYL-ACETATE METHANOL
( 338.0 K)
( 321.5 K)
( 331.0 K)
328.1 K
Azeotrope
Feed 1
D1, Feed 2
B1
D2
B2
mixer S1
S2
S3
B1
D1
D2
B2
B3
D3
B3D3
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 42
Another flowsheet configuration: High boiling azeotrope
Identify the azeotropes, determine the distillation boundaries,
generate the residue curves, design and analyze the separation
scheme
How to identify feasible configurations & design?
12
3
4
5
feed
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 43
Other flowsheet configurations
A, B, Solvent
A, Solvent
B
Solvent
A
For different types of
ternary diagrams, the
flowsheet can be fixed in
advance, consisting of
minimum two
distillation columns.
What kind of distillation
boundary and residue
curves are needed to get
the flowsheet shown on
the right?
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 44
Part-IV: Other separation processes
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 45
46
Graphical Design Technique
Draw the ternary LLE
diagram
Locate F (feed) & S
(solvent) streams & join
them in a straight line
Locate any point M that
determines the mixing
point between F and S.
Locate a tie-line that
passes through M. The
end-points of the tie-line
indicates the composition
of E and R streams
M
R
E
F
S
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Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 47
Graphical Design Technique for LL-extraction
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Modelling and design of counter-current LL-extraction systems
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Binary T-x diagram
Ternary saturation diagrams at
constant T & solvent-free
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 50
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 51
Equipment design parameters
(to be covered in next lecture)
52
• Distillation Column Design - Determine, Reflux ratio,
Number of stages, Column diameter, Tray height, Heat
duties for reboiler & condenser (following the example in
the book)
• Use the lk/hk, lk, hk to calculate Ni & Ri
• Calculate Nt = 0.8 maxi(Ni) + (1-0.8) mini(Ni); use efficiency of 80%
• Calculate R = 0.8 maxi(Ni) + (1-0.8) mini(Ni)
• Calculate L´ and V´ and from it, Flv
• Use Flv and Fig 4.4 to obtain Csb,t (for a selected tray spacing)
• Calculate flooding velocity, Unf, and from it, the area A and
diameter D of the column (use Eqs. 4.7 or 4.8 and 4.9)
• Determine Tray stack height, extra feed space, disengagement
space (top & bottom), skirt height
• Qcond = HV V – hL L
• Calculate Qreboil from total energy balance
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 53
• Distillation Column Design - Determine, Reflux ratio,
Number of stages, Column diameter, Tray height, Heat
duties for reboiler & condenser (Using PRO-II)
• Use Short-Cut Fractionation (for column design)
• Use rigorous simulation model to obtain the final design
• Use the “sizing” calculation option for the column design
• Select the column diameter, tray spacing, etc., from the output of
PRO-II
• For condenser duty = Qcond (given by PRO-II), size a heat
exchanger (determine area A)
• For reboiler duty = Qreboil (given by PRO-II), size a heat exchanger
(kettle-type) – determine area
• Determine Tray stack height, extra feed space, disengagement
space (top & bottom), skirt height
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 54
• Absorption Column Design - Determine, absorption
factor, Number of stages, Column diameter, Tray height,
Heat duties for reboiler & condenser
• Use the lk/hk, lk, hk to calculate Nt
• Calculate Nt from Kremser equation (approx = 10)
• Use efficiency of 20%
• Calculate L´ and V´ and from it, Flv
• Use Flv and Fig 4.4 to obtain Csb,t (for a selected tray spacing)
• Calculate flooding velocity, Unf, and from it, the area A and
diameter D of the column (use Eqs. 4.7 or 4.8 and 4.9)
• Determine Tray stack height, extra feed space, disengagement
space (top & bottom), skirt height
• Packed columns can also be calculated from the number of
transfer units and height of transfer units
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 55
• Pumps, Compressors, Heat Exchangers, ….
• The sizing parameters for each of these equipments can be
obtained from PRO-II or calculated through the method
used in the book (see the ethanol case study in chapter 4)
• Pump – find the power needed (based on work)
• Compressor - find the power needed (based on work)
• Tank – volume (area and height) based on residence time
• Heat Exchangers – area of the heat exchanger based on U,
T, Q, Flowrate
• …..
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 56
•We have now
performed mass and
energy balance.
•We have added
pumps/compressors,
heat exchangers
wherever necessary.
•Now we need to do the
sizing calculations for
all unit operations in
the flowhseet.
•Costing & Economic
analysis
•Ethanol Process: Case Study (from Textbook)
Course: Process Design Principles & Methods, L6 PSE for SPEED, Rafiqul Gani 57
• Prepare a list of unit operations found in the flowsheet
• For each unit operation, find a design that matches the
calculated input-output conditions to obtain the sizing
parameters
• Use the sizing parameters to determine the cost of each
unit operation
•Decisions that need to be made
•Choice of equipment type
•Choice of pressure (already made)
•Choice of material
•Other parameters specific to the unit operation
•Sizing & Costing Calculations