group8 presentation
TRANSCRIPT
CL-304 (PED-II) Instructor: Prof. Ashok Kumar DasmahapatraGroup 8
PROCESS EQUIPMENT DESIGNTERM PROJECT
Process & Mechanical Design of a Packed Bed Extractor
Group Members:Namrata Das (130107034)Nayan Gupta (130107035) Nilesh Raj (130107036)Niraj Chetry (130107037)
Problem Statement:
Extraction of Benzene is desired from a mixture of Benzene & 1-Hexene containing 78 mole% 1-Hexene and 22 mole% Benzene.
Flow rate of the feed solution is 6000 kg/hr.
Tetra-methylene Sulphone is to be used as the solvent for 96% extraction of benzene from the feed mixture.
Ternary equilibrium data:
Description:
Materials:Carrier : 1-Hexene (A)Solvent: Tetra-Methylene Sulphone (B) Solute : Benzene (C)
Continuous Phase Properties:Density (ρc) = 715.73 kg/m3 Viscosity (µc) = 4.7x10-4 Pa.sDiffusivity of Benzene (Dc) = 1.62x10-9 m2/s
Dispersed Phase Properties: Density (ρd) = 1261 kg/m3 Viscosity (µd) = 0.013 Pa.sDiffusivity of Benzene (Dd) = 4.1x10-9 m2/s Interfacial tension of dispersed phase (γ) = 0.00728 N/m
Solution Procedure: Process calculations
1. Equilibrium Curve:o Plot the right-angled ternary plot
2. Raffinate & Extract Phase Mass Flow Rates:o Use stoichiometric calculations to find these two
3. Minimum Solvent Rate:o Calculate the minimum solvent rate for extraction by locating Δm on the ternary plot
4. Equilibrium Solute Concentration in Extract:o Total material balance & solute balance gives => yE
5. Packing Material Specifications:o Using 3 different types of packing material- Raschig Rings- Lessing Rings- Berl Saddles
(Image Source: Google Image Search)
6. Flooding Velocity:o The flooding velocity for the dispersed phase & continuous phase is calculated using
the correlation:
(Ref: A.Suryanarayna, page:551, for correlation)
7. Column Diameter:o Using flooding velocity & mass flow rate, find the column diameter
8. Dispersed phase hold-up (ф):o Solve the cubic equation - UD + UC (ф/1- ф) = Vo ε ф(1-ф); where, Vo = C[aP ρC / ε3gΔρ]-0.5
to get the values of фo Select the root such as ф <0.52
9. Mass Transfer Coefficient (Koca):o Calculate Schmidt’s No. for both phases and use packing specifications and the above
value of ф along with the avg. coefficient distribution(m) from equilibrium data to calculate Koca
Solution Procedure: Process calculations
10. Height of Transfer Units (HtoC):o Using continuous phase velocity (UC) & mass transfer coefficient (Koca) to get HtoC
11. No. of Transfer Units (NtoC):o Using yE found from material balance and xF* found from the equilibrium curve, find
NtoC using the following: NtoC = xRʃxF dx/(x-x*) ~ (xF-xR)/(x-x*)M
where, (x-x*)M = [(xF-xF*)-(xR-xR*)]/[ln(xF-xF*)/(xR-xR*)]
12. Column Height:o Using the above two values of HtoC & NtoC , we get the column height: H = HtoC * NtoC
13. Comparison of Packing Materials:o We repeat the steps 1-11 for each of the packing material type and tabulate the results to compare all 3 types of material choice:
It is evident from the calculated results that “Lessing Rings” would be the optimum choice as a packing material for the desired extraction
Solution Procedure: Process calculations
Mechanical Design: Specifications
Diameter of the tower, Di =1mHeight of the tower, H = 2.9mWorking Pressure = 1atm =10.1325 kg/cm2= 0.101325 MPa Design Pressure, P = 1.13atm = 11.4497 kg/cm2= 0.114497 MPaShell Material: Plain Carbon Steel, Grade 2B (IS : 2002-1962)Permissible Tensile Stress, ft = 950 kg/cm2 ~ 95 MPaInsulation thickness = 100mmDensity of insulation = 770 kg/m3
Top disengaging space= 1mBottom separator space= 1mDensity of material of column = 7700 kg/m3
Wind Pressure = 130 kg/m2 ~ 1.275MPa
Mechanical Design: Calculations
1. Shell Thickness: o Using the formula: ts = PDi/(2fJ+P) + c , we get the shell thickness
2. Head Design:o Working Pressure Range: 0.1~1.5 MPa Choice of Head: Shallow dished & Torispherical We calculate the thickness of head by: t= PDoC/2fJ
3. Stress calculations: o Stress in the mechanical design due to various contributors are calculated: Axial Stress (compressive): fap= PD/4(ts-c) Compressive stress due to weight of shell upto a distance ‘x’ : fds=ρsgx Compressive stress due to weight of insulation: fd(ins)= ᴨDinstinsρins / ᴨDmt Compressive stress due to weight of liquid and tray: fdl= Wliq/ ᴨDm(ts-c) Stress due to weight of attachments: fd(att)= Wa/ᴨDmt Total compressive dead weight stress at height ‘x’: fdb= fap+fds+fd(ins)+fdl
Stress due to wind load at distance ‘x’: fws= 1.4Pwx2/ ᴨDot Stress in upwind side: fmax=fws+fap-fds
Stress in downwind side: fmax=fws+fap+fds
Calculating the failure location ‘x’ verifies the earlier calculated value of “Column Height”
Mechanical Design: Specifications
4. Internal Packing Support:o For column diameter upto 1.2m, we can use the GIS/EMS Random Packing Support
Grid in such small columns
(Ref: Internals for packed column, SULZER Chemtech)
5. Distributor:o For low interfacial tension value in LLX, Extraction Distributor VRX can be used.
(Ref: Internals for packed column, SULZER Chemtech)
Results: Design Details
The design specifications based on the optimum choice of packing material are listed below:
Graph:
Bibliography:
Mass Transfer Operations, 3e, Robert E. Treybal Mass Transfer Operations, A. Suryananarayana Mass Transfer Operations, B.K.Dutta Packed Tower Design & Applications, Ralph F. Strigle Perry’s Handbook, 8th Edition, Section-15, Mc Graw Hill Education Packed Column Design & Performance, L.Klemas & J.A.Bonilla Structured Packings: for Distillation, Absorption & Reactive Distillation, by SULZER Chemtech Ltd. Liquid-Liquid Extraction Technology, by SULZER Chemtech Ltd. Design Practice for Packed Liquid-Liquid Extraction Column, by SULZER
Chemtech Ltd. Internals for Packed Columns, by SULZER Chemtech Ltd.