1. Review of Separation Unit Ops
Holly Barra
Simone Gelinas
Franklin Ning
Max Pereboom

2. Agenda What is separations? Types of separations?
Three separation operations present in Hydrocarbon Formation

3. What are separations processes?
Pure products are valuable!
Side reactions and excess reactants lead to impure products
Separations are used to separate unwanted components
These can be disposed of, sold, or used as recycle

4. Definitions
Split Fractions (i.e. recovery)
Separation Factor

5. Intro to Separations in Hydrocarbon Formation
drums

6. Liquid-Solid Separation Unit Ops
Considerations: Solids concentration, feed rate, nature of solid particles, and objective (recovery, degree of dryness)

7. Filtration Passing slurry through porous filter medium
Key Terms: Filtrate (Permeate) and Retentate
Cross-Flow Filtration
Batch
Nutsche (Gravity and Vacuum)
Plate and Frame Press (Pressure)
Leaf Filters (Pressure and Vacuum)
Rotary Drum Filters (Usually Vacuum)
Continuous
Disc Filters (Pressure and Vacuum)
Belt Filters (Vacuum)
Horizontal Pan Filters (Vacuum)
Centrifugal Filters
Cross-Flow Filters
Source: LiqTech International

8. Common Types of Gas-Liquid Separation
Phase Addition/Creation
Flash Drums (Liquid --> Vapor)
Absorption (Vapor --> Liquid)
Stripping (Liquid --> Vapor)
Distillation (Liquid and/or Vapor --> Liquid and/or Vapor)
Separations Process Principles (Textbook)

9. Common Types of Gas-Liquid Separation (Cont’d)
Barrier
Osmosis (Liquid across nonporous agent)
Gas Permeation (Vapor across nonporous agent)
Solid Agent
Adsorption (Vapor or Liquid separated by solid)
Chromatography
Ion Exchange
Force Field or Gradient
Centrifugation
Electrodialysis
Separations Process Principles (Textbook)

10. Flash Drums (or Knockout Drums)
Purpose: Separate entrained liquid droplets from vapor streams
Method: Use gravity to settle the liquid
Types: Vertical & Horizontal Drums
Modifications: Demisters improve separation performance (esp. for small droplets)

11. Designing Vertical Flash Drums
Solve for settling velocity ut
Solve for minimum vessel diameter Dv
Calculate liquid depth hL for holdup time of 10 minutes (ensure suitable vessel sizing)
Spacing b/t the inlet and hL allows for surges and positioning of level controller
Chemical Engineering Design, Principles, 2nd Edition (Textbook)

12. Designing Horizontal Flash Drums
Vessel diameter cannot be determined independently from length
Vapor residence time for liquid settling
Liquid holdup time requirements
See pg. 772 Design Textbook for calculation examples
Most economical Lv/Dv ratio depends on operating pressure
Vessel diameter and length must be chosen to give sufficient residence time for liquid droplets to settle out and for required liquid holdup to be met
Chp 14 of Design book discusses Op Pressure
Chp 16 of Design book walks through calculations
Chemical Engineering Design, Principles, 2nd Edition (Textbook)

13. Flash Drums in Diesel Production

14. Flash Drums in Diesel Production
Separates out the vapors before entering column etc.
Reduces vapor loading to avoid flooding
Prevents higher heater firing and pressure drops
drums

15. Distillation Purpose: Separate components based on volatility
Method: Selective evaporation and condensation
Types: Batch & continuous
Applications: Alcohols, fossil fuels, atmospheric gases

16. Designing Distillation Columns
Plot equilibrium data
Plot operating lines & q line
Count steps between operating line and equilibrium data from xd to xb
This is the required number of stages

17. Sizing and Pricing Distillation Columns
Smaller is cheaper!
Fewer trays means less height
Diameter is determined by vapor velocity and tray spacing
Spacing is usually around 2ft but can be changed to minimize shell volume
Trays also cost money

18. Useful Resources Solid Liquid Separators: Towler Chapter 18.6
Liquid Vapor Separators: Towler Chapter 16.3
Liquid Liquid Separators: Towler Chapter 16.4
Distillation Columns: Towler Chapter 17