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

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

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

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

Intro to Separations in Hydrocarbon Formation http://www.orioninstruments.com/petroleum-refining#preflash drums

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

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

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)

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)

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) https://en.wikipedia.org/wiki/Flash_evaporation

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)

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)

Flash Drums in Diesel Production

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 http://www.orioninstruments.com/petroleum-refining#preflash drums

Distillation Purpose: Separate components based on volatility Method: Selective evaporation and condensation Types: Batch & continuous Applications: Alcohols, fossil fuels, atmospheric gases http://controlguru.com/distillation-introduction-to-control/

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 http://www.slideshare.net/alsyourih/design-of-packed-columns

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 http://www.wikiwand.com/en/Fractionating_column

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