Download - CSTR by Asif
1
Advisor:Professor Dr.A.R.Saleemi
Co Advisor:Hafiz Zaheer Aslam
2
Group Members
Asif Masih Sharazi 2005-Chem-61
Mohammad Mohsin 2005-Chem-75
Saadi Hassan Mufti 2005-Chem-109
Saira Rasheed Khan 2005-Chem-29
Sundus Fatima 2005-Chem-43
3
Presentation ContentsProcess DescriptionDesign of CSTRDesign of SeparatorDesign of AbsorberDesign of Heat ExchangerDesign of Distillation Column
4
Equipment Coding
R = ReactorE = Heat ExchangerC = ColumnP = PumpM = MixerV = Vessel
5
6
7
Selection of ReactorReaction KineticsVolume of CSTRSelection of agitatorWall thicknessHead thicknessJacket area
8
Selection of ReactorType of reactionTemperature and pressure of reactionNeed for removal or addition of reactants and productsCatalyst use considerationRelative cost of reactorAvailable space Safety
9
10
11
12
0.02< <2 and E =1 Reaction takes place in the liquid phase Reaction is moderate
These conditions requires High interfacial area High liquid hold-up
To fulfill these requirements CSTR is the best
Ref:Coulson, Richardson, Chemical Engineering, Butterworth-Heinemann, Vol: 3, Edit: 3, (196-212), 1994.
13
Advantages of CSTR Very less chances of coalescence High liquid hold up High interfacial area Less resistance in gas diffusion
Bubble Column: Greater chances of coalescence
Packed Bubble Column: Greater pressure drop
Ref:Coulson, Richardson, Chemical Engineering, Butterworth-Heinemann,
Vol: 3, Edit: 3, (196-212), 1994.
14
Chemical Reaction CH3COOCH3+ CO (CH3CO)2
(CH3CO)2 + H2 CH3CHO + CH3COOH
Complete Reaction
CH3COOCH3+CO+ H2 CH3COOH+CH3CHO
Heat of Reaction 7.9x103 KJ/Kg mol
Catalyst CH3COOPd
15
160◦C
310.2KPa
Slow
Fast
16
310.2KPa160 ◦C
368KPa160 ◦C
310.2KPa160 ◦C
190◦ C1255.1Kpa
312Kpa25 ◦C
T=160°CP=310KPa
T=25°CP=312KPa
T=160°CP=368KPa
T=160°CP=310KPa
Reaction KineticsrB= (k1K1K2PBWA*)/(1+K1P+K1K1PA*)
k1 = Rate constantK1 = Adsorption coefficient for COK2 = Adsorption coefficient for H2
P = CH3I ConcentrationB = CH3COOCH3 concentrationW = Catalyst (CH3COOPd) concentrationA* = Equilibrium dissolved concentration of CO
Ref: Ashutosh, A.Kelkar, Rengaswamy Jaganathan, and Raghunath V.Chaudhari ,Industrial & Engineering Chemistry Research, ACS,Vol.40,No.7,2001
17
k1= 0.112 m3/Kgmol.sec
K1 = 1.75 m3/Kg mol
K2 = 2.86 m3/Kg mol
P = 0.09 Kg mol/m3
B = 0.09 Kg mol/m3
W = 8.89 Kg mol/m3
A* = 0.004939 Kg mol/m3
rB = k1K1K2PBWA*/(1+K1P+K1K1PA*)
= 0.0016 kg mol/m3.sec
18
Volume of Reaction Mixture
Vr/FBO = XB/rB
Vr = 21.2 m3
Ref: Octave Levenspiel, Chemical Reaction Engineering, Edition:3, (91-113)
19
Space time & Space Velocityτ = Vr/Vo
= 463 sec
s = 1/τ
= 2.16 x 10-3 sec-1
20
Length & DiameterLength and Diameter Calculation
V=(D2/4) x L
L/D = 1
So
L = 5.20m
D = 5.20m
21
Volume of ReactorIf Rated Capacity<1.89m3
Allowable head space is taken 15%
If rated capacity >1.89m3
Allowable head space is taken 10%
Allowable head space= 21.2 x0.1 = 2.12m
Reactor Volume = 21.2+21.12
= 23.32m3
Ref:Coulson, Richardson, Chemical Engineering, Butterworth-Heinemann, Vol: 3, Edit: 3, (196-212), 1994.
22
Selection of Agitator
Factors affecting the selection
Mixing pattern(axial, radial)Capacity of vesselDensity and viscosity of fluid viscosity
23
Three basic types of Impeller
1.Flat blade (Rushton) turbines(Suitable for shear controlled processes)
2.Propeller and Pitched blade turbines(suitable for bulk fluid mixing)
3.Anchor and Helical ribbon agitators90Suitable for highly viscous fluids)
Ref: Coulson, Richardson, Chemical Engineering, Butterworth-Heinemann, Vol: 3, Edit: 3, (196-212), 1994.
24
Agitator DesignFor turbine agitatorDa/DT = 1/3 , Da = Impeller diameter
J/DT = 1/12 , J = Width of Baffles
W/Da = 1/5 , W = Impeller Width
La/Da = 1/4 , La = Length of Impeller blades
E/DT = 1/3 , E = Impeller Height above vessel floor
25
Da/DT = 1/3 , Da = 1.73m
J/DT = 1/12 , J = 0.43m
E/DT = 1/3 , E = 1.73m
W/Da = 1/5 , W = 0.35m
La/Da = 1/4 , La = 0.43m
26
Power Calculation
Re = Da2 NP /
= 8.37 x 106
Np = KT Reb Frc
NP = KT = 6.30
P = NpDa5N3/g
= 7290W
= 9.8hp
27
28
Material of ConstructionFactors affecting the selection of material1. Mechanical properties such as tensile strength2. The effect of high and low temperatures on the
mechanical properties3. Corrosion resistance4. Any special properties required; such as thermal
conductivity, electrical resistance, magnetic properties5. Ease of fabrication-forming, welding, casting 6. Availability in standard sizes-plates, sections, tubes7. Cost
29
Austenitic Stainless Steel High Tensile StrengthHigh Corrosion resistance
Material Specification IS:1570-1961
Designation:
Cr=19% Ni=9%
Mo=3% Ti=20%
Ref: Bhattacharyya, Chemical Equipment Design Mechanical Aspects,CBS,Edition:1,(261-265),2001
30
Design TemperatureThe strength of metals decreases with
increasing temperature so the maximum allowable design stress will depend on the material temperature.
The design temperature at which the design stress is evaluated should be taken as the maximum working temperature of the material.
We chose austenitic stainless steel for the fabrication of CSTR for which the design stress is evaluated at 200C. So the Design temperature of the CSTR is 200C.
31
Design PressureThis is normally be 5 to 10 per cent above the normal
working pressure, to avoid spurious operation during minor process upsets.
When deciding the design pressure, the hydrostatic pressure in the base of the column should be added to the operating pressure, if significant.
Ref: Coulson, Richardson, Chemical Engineering, Butterworth-Heinemann, Vol: 3, Edit: 3, (807), 1994.
32
PHydrostatic = g h
= 56259.8Pa
= 56.3KPa
POperating = 56.3+310.2
= 366.5KPa
PDesign = 366.5+(366.5 x 0.05)
= 384.83 KPa
33
Wall ThicknessThe thickness of process vessel is chosen so that it is not
only adequate against the induced stresses caused by internal pressure, but also ensures safety against stresses caused by extraneous agencies.
The thickness of wall depends on the pressure and temperature of vessel.
34
tw = P Di/(2fJ-P)
tw = wall thickness
P = design pressureDi = inner diameter of vessel
f = allowable design stress for material specified
J = joint efficiency factortw = 8.86 x10-3m = 8.86mm
Standard plate thickness = 9mm
35
Selection of HeadFactors affecting selection of Head Process temperature and pressureNature of the materials to be handledPosition of the vessel(Horizontal or vertical)Nature of the support Economy
Ref: Bhattacharyya, Chemical Equipment Design Mechanical Aspects,CBS,Edition:1,(39-42),2001
36
Head Type Characteristics
Flat High discontinuity stresses , high material cost
Ellipsoidal Suitable for pressure above 1.5MN/m2
Hemispherical Suitable for heavy duty high pressure vessels, most expensive
Conical Suitable for removal of solids from process vessels, commonly used ads reducers
Torispherical Suitable for low pressure vertical vessels
37
Head Thickness
tH = P Do C/2fJSolution of above equation will require iteration because ‘C’(stress concentration factor) is a function of ‘tH’.
ri = 0.06 x Do
assume Ri = Ro = Do
Ref: Bhattacharyya, Chemical Equipment Design Mechanical Aspects,CBS,Edition:1,(51-56),2001
38
ho = Ro –[( Ro - Do /2) x (Ro + Do/2 – 2ro )]1/2
= 0.88m
Do2/(4Ro) = 1.302m
(Do ro/2)1/2 = 0.903m
Effective external height of head
hE = 0.903m
hE/Do = 0.17
39
tH/Do = PC/2fJ = 1.704 x 10-3C
By iteration
C=1.32 and tH/Do = 0.002
tH = 11.9 x 10-3m
= 11.9mm
Standard sheet available is of thickness12mm
40
Torispherical Head
41
Jacket Area
42
Area of Jacket = п Di L + п Di2/4
As L=Di so
Area of Jacket = 5 п Di2/4
= 106.13m2
Jacket Temperature = 14°CReaction Temperature = 160°CHeat Duty of CSTR = 6.5 x 106 KJ/h
Ref: D.Q.Kern, Process Heat Transfer, (716-720, 791-846)
43
Heating Media = Water at 10°C
Heat Transferred through jacket
Qj = Uj Aj (Tj-TR)
= 3.16 x 107 KJ/h
Qj > QR so only jacket is enough to provide the required heat to maintain the temperature at 160°C
Ref: Harry Silla, Chemical Engineering Design and Economics, Library of Congress Cataloging-in-Publication Data, (240,375-394), 2003.
44
Specification SheetItem CSTR
Number of Item 1
Item Code R-100
Capacity 23.32m3
Operating Temperature 160◦C
Operating Pressure 366.5KPa
Length 5.20m
Diameter 5.20m
Impeller Diameter 1.73m
Wall thickness 9 x 10-3m
Material of Construction Austenitic Stainless Steel
Head type Torispherical
Head thickness 12 x 10-3m
Jacket area 106.13m245