Topics covered

Module aims
To introduce the principles of diffusional separation processes and describe mathematical and graphical methods for process and plant analysis and design.

Learning outcomes
At the end of the module, you should be able to:
• Describe qualitatively and model quantitatively the operation and design of economically viable processes and equipment for diffusional separation of binary mixtures or one-component transfer.
• Distinguish between staged and continuous separation equipment and apply the appropriate analysis and design techniques.
• Perform economic and sensitivity analyses during the process of equipment design.
• Solve problems related to:
- vapour-liquid equilibrium in binary mixtures
- flash distillation
- continuous distillation in plate or packed columns
- batch distillation in plate or packed columns
- absorption and stripping of dilute solutes in both plate and packed columns
- liquid-liquid extraction in single-stage mixer settlers and both cross-current and counter-current cascades
- the design of distillation/absorption/stripping columns

Module aims
To provide a general introduction into the processes of heat and mass transfer and aims to equip students with the knowledge and skills necessary to perform simple design and process calculations for a range of common industrial heat and mass transfer equipment.

Learning outcomes
At the end of the module, you should be able to:
• Solve steady state, uni-dimensional conduction problems for planar, cylindrical and spherical geometries, including multi-layer systems, systems where thermal conductivity varies with temperature and simple problems with heat generation.
• Solve simple 2-d conduction problems using the graphical method.
• Solve simple transient conduction problems.
• Solve simple boundary layer problems, e.g. the calculation of b.l. thicknesses for different velocity profiles.
• Estimate heat and mass transfer coefficients for a range of convective transport applications by selection and manipulation of appropriate correlations.
• Estimate overall coefficients of heat and mass transfer from individual coefficients, plus fouling and wall resistance in the case of heat transfer and an equilibrium line in the case of mass transfer.
• Solve heat exchanger sizing problems using the “log mean temperature difference” approach, including selection of sensible dimensions, tube size and number for shell-and-tube exchangers.
• Solve heat exchanger rating problems using the “effectiveness approach”.
• Calculate mass transfer rates for simple systems using Fick’s Law, in its several forms.
• Calculate mass transfer rates in simple binary systems in which molecular diffusion is superimposed on bulk flow, e.g. diffusion-controlled reaction at a catalyst surface.
• Calculate molecular diffusivity from the Stefan Tube technique, given appropriate data.

Precursor: Process Analysis
1. Lecture 2,3: Unit Conversion
a. Problem Sheet 1
2. Lecture 4: Economic Potential
3. Lecture 5,6: Mass balance no reaction
4. Lecture 7: Recycle
5. Lecture 8: Strategy
6. Lecture 9,10,11,12,13: Reactive systems, DoF, Strategy
a. Problem Sheet 2
7. Lecture 14,15,16: Enthalpy change
8. Lecture 17,18: Energy balance no reaction
9. Lecture 19,20: Energy balance reactive systems
10. Lecture 21,22: Mass and energy balances combined
a. Problem Sheet 3
11. Lecture 23,24,25,26: VLE and phase diagrams
a. Problem Sheet 4,5
12. Lecture 27,28,29: Environmental and impact assessment

Separation Processes I
1. Introduction
a. Plan
b. Objective
c. Reading Materials
d. Separation types and examples
e. Example in UG teaching lab
2. Vapour-Liquid Equilibrium
a. Phase rule, degrees of freedom
b. T,x,y and P,x,y, diagrams, Raoult’s law relative volatility
c. Q-line
d. Azeotropes
e. Problem 1
3. Flash Distillation
a. Degrees of freedom
b. Numerical Solution
c. Graphical Solution
d. Energy Balance and H,x,y diagram
e. Cascade flash to distillation
f. Problems 2,3
4. Distillation and the McCabe-Thiele Construction
a. Plate distillation
b. McCabe-Thiele
c. Rectifying line
d. Stripping line
e. Full Construction
f. Single plate mass and energy balance
5. The Feed Line
a. Example
i. Equilibrium Curve
ii. Construction
iii. Plot in Excel
iv. Feed line analysis
6. Reflux Ratio
a. Nmin limit and Fenske’s equation
b. Rmin limit
c. Operating R
d. Condenser and reboiler types
e. Problems 5,6
7. Further Discussion of the McCabe-Thiele Method
a. Multiple feeds and products
b. Steam injection
c. Special and twin column
d. Efficiency
e. Problems 7,8
8. Distillation of Non-Ideal Systems
a. Pinch point
b. Material and energy balance
c. Nmin
d. Rmin
9. Batch Distillation
a. Differential distillation and Rayleigh equation
b. Batch distillation column
c. Example
d. Problems 9,10
10. Distillation Column Design
a. Tray design
b. Entrainment
c. Pressure drop
d. Example
11. Absorption and Stripping of Dilute Mixtures (mainly Absorbers)
a. Counter current column
b. Henry’s law and equilibrium line
c. Operating line and minimum line
d. Example
12. Further Analysis of Absorption and Stripping Processes (mainly Stripper)
a. Operating line and diagram
b. Example stripper
c. Kremser method
d. Example absorption
e. Efficiency
f. Problems 11,12
13. Liquid-Liquid Extraction
a. Single stage mixer
b. Analytical and graphic solution
c. Example single stage
d. Cascade Co/Cross/Counter example and comparison
e. Problems 13,14
14. Interfacial Mass Transfer
a. Molecular diffusion, UMD, and EMD
b. Two film theory
15. Absorption and Stripping in Packed Columns
a. Packing
b. Absorber and stripper mass balance
c. Packing height
d. Number of transfer units
e. Operating line
f. Graphical solution
g. Problem 15
16. Further Analysis of Separations on Packed Columns
a. Analytical methods of strippers and absorbers
b. Reactive columns
c. Example reactive column
d. Packed distillation column
e. Column diameter
f. Example packed distillation

Written examination – feedback will be given while you are at Imperial in week four

1. Course introduction and mathematics recap
2. Problem sheet 1 – Applying maths to problems
3. Energy balances and conductive heat transfer
4. Problem sheet 2 – Energy balances and heat conduction
5. Solving conductive heat transfer problems
6. Problem sheet 3 – Temperature profiles in heat conduction
7. Diffusive mass transfer and concentration profiles
8. Problem sheet 4 – Derivations and applications of diffusive mass transfer
9. Transient heat and mass transfer
10. Problem sheet 5 – Application of the Fourier series in transient problems
11. Convective heat and mass transfer
12. Problem sheet 6 – Application of dimensionless analysis
13. Convection and conduction
14. Problem sheet 7 – Fluid flow and heat and mass transfer
15. Heat exchangers
16. Problem sheet 8 – Heat exchanger units, fouling and temperature profiles
17. Mass transfer units and mass transport in biological systems
18. Problem sheet 9 – Haemodialysis

Written examination - please note that this will be on your final day and feedback will therefore be emailed to you as soon as possible afterwards.