1 / 18

CHEMCAD Seminar Mass Transfer 2 John Edwards, P&I Design Ltd January, 2015

CHEMCAD Seminar Mass Transfer 2 John Edwards, P&I Design Ltd January, 2015. www.chemstations.com. MASS TRANSFER – ABSORPTION SESSION OBJECTIVES. SIMULATION SUITE. CHEMCAD SOFTWARE. www.chemstations.com. www.chemcad.co.uk. Basic Theory Thermodynamics CO 2 Amine System

susancoleman
Télécharger la présentation

CHEMCAD Seminar Mass Transfer 2 John Edwards, P&I Design Ltd January, 2015

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHEMCAD Seminar Mass Transfer 2 John Edwards, P&I Design Ltd January, 2015 www.chemstations.com

  2. MASS TRANSFER – ABSORPTIONSESSION OBJECTIVES SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk • Basic Theory • Thermodynamics CO2 Amine System • Carbon capture simulation • Design considerations

  3. MASS TRANSFER - ABSORPTIONBASIC THEORY ENHANCEMENT FACTOR SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Henry’s Law where m is slope of equilibrium line H=2950 bar for CO2 Stripping Factor CHEMCAD AMINE HG only Transfer Unit relationships reduces influence of liquid film Enhancement Factor E increasing E same as increasing PT Stripping Factor Mass Transfer Coefficients

  4. MASS TRANSFER – ABSORPTIONCASE 8.01 CO2 ABSORPTION IN MEA SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case 8.01 page 291 - 294

  5. MASS TRANSFER – ABSORPTIONCASE 8.01 COLUMN OPERATION SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case 8.01 page 291 - 294

  6. MASS TRANSFER – ABSORPTIONCASE 8.01 PACKED COLUMN SIZING SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case 8.01 page 291 - 294 HTU OV

  7. MASS TRANSFER – ABSORPTIONPOST COMBUSTION CO2 / MEA SYSTEM SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case 14.05 page 500 - 502 Cooled flue gas at 100°C is fed to an absorber re-circulating 30% MEA solution to absorb CO2 CO2 rich bottoms is fed via a cross heat exchanger for heat integration to a steam stripper

  8. MASS TRANSFER – ABSORPTIONPOST COMBUSTION CO2/MEA PARAMETERS SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case 14.05 page 500 - 502

  9. MASS TRANSFER - ABSORPTION PROCESS REVIEW SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk • Classification • Physical - exploits differences in physical properties • vapor pressure, solubility, molecular geometry, surface activity • Chemical - based on reaction kinetics and interfacial model • Mixture Classification • Homogeneous (V/L/S) - single phase gas or liquids • Air • Miscible Solvents • Heterogeneous (V/L/L/S) - immiscible phases • Liquid + Liquid • Liquid + Gas • Select Separation Process • Physical Absorption – Thermal Stripping • Reactive Absorption • Select Separating Agent • Solvent for Absorption • Stripping Method • Design Phases • Conceptual • Detailed • Final validation and release for construction

  10. MASS TRANSFER - ABSORPTION DESIGN PRINCIPLES SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk • Extent of separation • Number of equilibrium stages, predictable with reasonable confidence • Concept methods - Kremser equation, independent calculation • Rigorous methods - computer simulation, manufacturer’s software • Time of phase contact • Rate = (Driving Force) / Resistance • Driving Force = Departure from Equilibrium (Post combustion CC small) • Resistance (difficult to predict) • operating conditions: T, P, composition • physical properties of both phases • interfacial reaction mechanism • velocity, flow regime • Permissible pressure drop • Sets column diameter • Energy requirements • Heat • Heating and cooling • Heat of solution effects • Mechanical/Electrical • Prime movers for gas & liquids

  11. MASS TRANSFER - ABSORPTION DESIGN PROCEDURE SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk

  12. MASS TRANSFER - ABSORPTION COLUMN DESIGN INTERNALS EFFICIENCY SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk • Tray Column Murphree • Apply efficiency factor to theoretical plate • Obtain actual column profile for desired recovery • Apply safety factor for final number of trays • Packed Column Height Equivalent of Theoretical Plate (HETP) • Determine theoretical stages for desired separation • Obtain column profile • Multiply by HETP to get total height of packed section • Difficult to predict Murphree or HETP from theory • Depends on contacting device, phase equilibrium, hydraulics • Experimental data and correlations • Vendor information

  13. MASS TRANSFER - ABSORPTION COLUMN DESIGN CONSIDERATIONS Weeping Flooding SIMULATION SUITE CHEMCAD SOFTWARE Liquid weeps at low gas velocity Liquid flow reverses at high velocity www.chemstations.com www.chemcad.co.uk • Column diameter is chosen to provide flexible operation between flooding and weeping. Typical operating range 60 to 70% of the flooding velocity. • The flooding velocity is determined by correlations. • Approach to flooding is used to get actual superficial velocity based on column diameter. • Minimum velocity to prevent plate weeping and wetting rate for packing • Plate column down-comers take up about 5-20% of column area • Packed columns require height allowance for liquid distribution and redistributors

  14. MASS TRANSFER - ABSORPTION DESIGN TRAY COLUMNS SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk • CHARACTERISTICS • Predictable hydraulic and mass transfer behaviour • Moderate to high pressure drop per tray • Can be scaled to large diameters • Suitable for fouling service • Feed point flexibility is easy • SPECIFICATION • Number of actual stages by applying Murphree plate efficiency • Feed tray location • Type of trays, tray spacing, tray layout • Column diameter • Column height • Feed / Side take-off arrangements / Nozzle sizes • Reboiler / Condenser sizing • COLUMN HEIGHT • Number actual stages x tray spacing + space allowance for feed/draws + sump + top volume • Tray spacing for most applications is 18-24 inches • Rule of thumb could be to add 1- 2 nozzle diameters to the total height for feeds and draws • Sumps sized on liquid residence time. Two to five minutes is reasonable.

  15. MASS TRANSFER - ABSORPTION DESIGN PACKED COLUMNS SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk • CHARACTERISTICS • Low pressure drop / smaller diameter / Feed point fixed • Random packing scale-up for HETP is difficult; structured packing scale-up is predictable • HETP prediction less well developed than for trays • Low to moderate cost for random packing; high cost for structured packing • Not suitable for fouling service • SPECIFICATION • Type of packing • Random packing • Structured packing • Trade-off pressure drop vs. HETP vs. cost • Column diameter – height of packing – feeds and off-takes • PACKED HEIGHT • HETP Replaces Tray Efficiency • Bed Height = No of Theoretical Stages x HETP • HETP is difficult to generalize and is a function of the type of packing, the system being separated and the hydraulics of the column. Experimental or vendor-supplied values are used.

  16. MASS TRANSFER – SOLVENT EXTRACTIONCOLUMN STAGE SENSITIVITY SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case Extraction Column Controller used to keep solvent feed at number of stages

  17. MASS TRANSFER – SOLVENT EXTRACTIONSENSITIVITY STUDY SIMULATION SUITE CHEMCAD SOFTWARE www.chemstations.com www.chemcad.co.uk Case Extraction Column

  18. MASS TRANSFER – ABSORPTIONDESIGN HEURISTICS Air / Gas Movers Pressure Rises Fans 12 in wg, blowers < 40 psig compressors > 40 psig Compressors: Reciprocating compressors: Efficiencies 65% at compression ratio of 1.5, 75% at 2.0 and 80-85% at 3-6 Efficiencies of large centrifugal compressors 76-78% and rotary compressors 70%. SIMULATION SUITE CHEMCAD SOFTWARE Centrifugal pumps: Single stage for 15-5000 gpm, 500 ft max head; Multistage for 20 – 11,000 gpm, 5500 ft max head. Efficiencies 45% at 100 gpm, 70% at 100 gpm and 80% at 10,000 gpm. www.chemstations.com www.chemcad.co.uk

More Related