1. A Review of Separation Topics
Group 6: Ben, Brendan, Sonia, Loyan, Eyuel

2. Overview of Topics: Different Types of Separation techniques
Brief Review of Thermodynamics
Overview of Mass Transfer Principles
Absorption/Stripping
Binary and Multicomponent Distillation
Liquid-Liquid Extraction/Membrane Separation
Conclusion

3. Different Types of Separation
1. Phase Creation (most common) Examples: - Distillation - Crystallization
2. Phase Addition Examples: - Liquid-Liquid Extraction - Absorption
3. Barrier Examples: - Reverse Osmosis - Gas Permeation
4. External Field Examples: - Electrophoresis (sep. by charge) - Centrifugation (centrifugal force)
Phase 1
Phase 1
Phase Creation
Barrier
Feed
Feed
Phase 2
Phase 2
Feed
Phase Addition
Phase 1
Phase 1
Feed
Force Field
Input-output control volume for phase separation
Input-output control volume for phase addition
Input-output control volume for barrier separation
Input-output control volume for external field separation
Mass Separating Agent
Phase 2
Phase 2

4. Review of Thermodynamics
T-x,y and P-x,y diagrams for a binary system.

5. Overview of Mass Transfer Principles
Fick’s Laws of Diffusion
High Concentration → Low Concentration
Mass transfers from areas of high concentration to low concentration.

6. Overview of Mass Transfer Principles
Steady state diffusion
Transient diffusion
Quasi-steady state
Chemical reactions
Convective mass transfer
Graphical representation of concentration changes with distance at steady state.

7. Overview of Mass Transfer Principles
Steady state diffusion
Transient diffusion
Quasi-steady state
Chemical reactions
Convective mass transfer
Concentration profiles of a change in concentration at transient conditions and quasi-steady state conditions.

8. Overview of Mass Transfer Principles
Steady state diffusion
Transient diffusion
Quasi-steady state
Chemical reactions
Convective mass transfer
A first-order chemical reaction with respect to species A.

9. Overview of Mass Transfer Principles
Steady state diffusion
Transient diffusion
Quasi-steady state
Chemical reactions
Convective mass transfer
Graphs and dimensionless quantities for determining the convective mass transfer coefficient.

10. Absorption/Stripping
Absorption (gas scrubbing): The process by which one or more species is transferred from the gas phase to a liquid solvent
Absorption is used to separate gas mixtures, remove impurities, or recover valuable chemicals.
The solvent is the separating agent.
Stripping: The operation of removing the absorbed solute from the solvent is called stripping.
Absorbers are normally used with strippers to permit regeneration (or recovery) and recycling of the absorbent.
In this case, the insoluble gas is the separating agent.

11. Absorption/Stripping: Physical Principles
Absorption and stripping units operate using equilibrium stages, where liquid and vapor are in contact with each other (assumed to be at equilibrium).
The Kremser Method is employed to estimating the minimum absorbent or stripping agent flow rate.

12. Absorption/Stripping: Physical Principles
Columns can either be packed or trayed, where the minimum number of stages is determined through either an algebraic or graphical method.
Murphree Stage Efficiency
For a packed column a rate based approach is used to determine the specifications of the column.
Packed-Height Equivalent to Theoretical Stages (HETP)
HOG (overall height of a gas transfer unit)
NOG (overall number of gas transfer units)

13. Absorption/Stripping: Industrial Example
In the pretreatment of natural gas in the processes to produce LNG, an amine solution is typically used to scrub acid gas (H2S, CO2).
The rich amine is then sent downstream to a stripping unit where the lean amine is regenerated.
Make-up water is often used to dilute the the rich amine, to a desirable weight percentage.

14. Distillation: Binary Systems
McCabe-Thiele Graphical method (trayed columns)
Most useful to find Nmin and Rmin
Equilibrium data is needed. Xd, Xb and Zf are usually known or specified. Then you have to calculate D and B through a mass balance. You can determine Nmin by stepping off stages from xd to xb in between the equilibrium line and the 45 degree line. To determine Rmin: Find the slope of the line that intersects the point where the q-line intersects the equilibrium curve. That is equal to R/(R+1) (Shown above). Then, given a multiple of Rmin to operate at, you can re-step off stages and find the actual number of stages required.
Seader, Separation Process Principles

15. Multicomponent Systems
FUG method (for multicomponent systems)
Fenske Equation for Min stages
Underwood Equation for min reflux
Gilliland Correlation for actual reflux ratio and number of stages
For Multicomponent Systems: Use the FUG method. The flowsheet gives a good idea of how the process works, but realistically this method is used for finding Nmin and Rmin and then plugging that into a process simulator such as aspen. Alpha m is the geometric mean of the relative volatilities of the heavy key and light key on the top and bottom stages.
Seader, Separation Process Principles

16. Multicomponent Systems
To Find Rmin:
Gilliland Correlation isn’t all that practical to use, you just select an appropriate multiple of Rmin and plug into Aspen
Seader, Separation Process Principles

17. Liquid-Liquid Extraction
The separation of a liquid feed with two or more components using a solvent.
Solvent dissolves one or more of the components to facilitate separation.
Example: Acetic acid/Water and Ethyl acetate
Equipment for extraction
Mixer-Settlers
Spray Columns
Packed Columns
Plate Columns
Seader, Separation Process Principles

18. Liquid-Liquid Extraction
Graphical methods
Hunter-Nash Graphical Equilibrium Stage
Number of Equilibrium Stages
Minimum Solvent to Feed ratio
Maximum Solvent to Feed ratio
Maloney-Schubert Graphical Equilibrium Stage
Seader, Separation Process Principles

19. Membrane Separation Mass Transfer Through Porous Membranes Permeance
Retentate
Permeate
Fick’s Law of Diffusion
Seader, Separation Process Principles
(top right) Input-output of control volume for a membrane separation process.
(bottom right) Tubular air membrane separator of oxygen and nitrogen.
(bottom left) Illustrations of varying porous media through which species diffuse through.

20. Work Cited Separation Process Principles, 3e, Seader et al