1 / 64

Dr. M.O. Garg Director Indian Institute of Petroleum (Council of Scientific & Industrial Research ) Dehradun

FUNDAMENTALS OF EXTRACTION SYSTEMS. Dr. M.O. Garg Director Indian Institute of Petroleum (Council of Scientific & Industrial Research ) Dehradun. SYMPOSIUM ON SOLVENT EXTRACTION REVISITED FEBRUARY 5 TH , 2010 IIChE (NRC) Auditorium NEW DELHI-INDIA. Outline of Presentation.

davida
Download Presentation

Dr. M.O. Garg Director Indian Institute of Petroleum (Council of Scientific & Industrial Research ) Dehradun

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. FUNDAMENTALS OF EXTRACTION SYSTEMS Dr. M.O. GargDirectorIndian Institute of Petroleum (Council of Scientific & Industrial Research )Dehradun SYMPOSIUM ON SOLVENT EXTRACTION REVISITED FEBRUARY 5TH, 2010 IIChE (NRC) Auditorium NEW DELHI-INDIA

  2. Outline of Presentation • Introduction • Phase Equilibria and Stage Calculation • Hydrodynamics and Mass Transfer • Design and Scale - up • Concluding Remark

  3. Introduction • Liquid extraction • Separation of components with an insoluble liquid. • Transferring solute distributes itself differently between the two liquid phases resulting in separation. Comparison with Distillation • Distillation • Products comprise essentially substances present in feed • Involves high temp. opns. • Independent unit opn. for separations requirement. • Extraction • New solutions are produced. • Done at suitably low temp. • Normally accompanied by Dist.orEvapn. for recovery.

  4. Introduction(Contd.) Comparison with Distillation • Distillation • May require large no. of theoretical stages. • Plate efficiencies can be as high as 90% • Separates substances which differ in their V.P. • Extraction • Requires typically 3-10 theoretical stages. • Low Plate efficiencies • Major constituents are chemically very different.

  5. Solvent Extraction • Solvent Extraction process can be broadly divided into two parts • Extraction • Solvent Recovery • While extraction controls yield and quality of products, solvent recovery controls utility consumption

  6. Extraction PROCESS FLOW SHEET Raffi- nate EXTRACT E X T C O L R W C SRC SOL R E G FEED LEAN SOLVENT

  7. Steps for Solvent Extraction Technology Development Selection of Solvent Experimental Data Generation (LLE and Mass Transfer) Generation of Phase Equilibrium Data / Physico -Chemical Properties Prediction / Correlation of Phase Equilibria Mass Transfer Studies Pilot Plant Studies/Scale-Up Process Simulation / Design Extractor Design Diameter Height Scale-up Solvent Recovery Optimization Other Considerations

  8. Solvent Selection Criteria Solvent is the heart of the extraction process and governs the economics of the process. Final choice of solvent will be a compromise between • Corrosiveness • Flammability • Toxicity • Stability • Compatibility with product • Availability and • Cost • Solvent Capacity • Solvent selectivity • Solvent recovery difficulties • Density difference between Dispersed and Continuous Phases • Interfacial tension • Boiling point

  9. Selectivity and Capacity data for typical solvents

  10. Solvent Design • The type of solvent for a particular application is always a matter of discussion • The design of solvent to meet desirable properties may be possible in future with the application of • understanding of intermolecular interactions • group contribution approach for properties estimation • Such developments lead to very cost effective design and offer attractive return on revamp of existing units

  11. Phase Diagram (Liquid- Liquid Extraction)

  12. Ternary Phase Diagram for Model Hydrocarbons

  13. NMP Extraction Phase Diagram • Use to optimise: • Temperature • Pressure • S/F • Product yield • Product Properties Extract 0.85 0.87 0.89 0.91 0.93 0.95 0.97 0.99 1.01 1.03 1.05 Sp. Gravity 6 2 1 Raffinate 3 4 5 10 20 30 40 50 60 70 80 90 NMP + Water Wt.%

  14. Phase Equilibria Measurements XiiI=XiiII • Thermodynamic modelling • Sources of data • In-house data generation (IIP) • Literature as published from time to time • DECHEMA • Most of the data reported in terms of concentration than activity coefficient • Scarcity of data - in-house generation of data with relevant feed/solvent Data Compilation Prediction

  15. Phase Equilibria-Measurements • Phase Equilibria with actual system in single stage still • Infinite dilution activity coefficient for simple feeds • It is usually difficult to check thermodynamic consistency of the measured data, hence data generation requires skills

  16. Experimental Data Generation LLE data Batch units ( Mixture Settler) Mass transfer data Extraction studies Packed extractor (34 mm dia, 1.5 m height) Solvent Recovery (Distillation) studies 1” diaOldershaw columns Up to 50 actual stages

  17. Phase Equilibria-Prediction Feed/product fluids are complex mixtures, need to be characterized • To predict phase equilibria • To understand physico-chemical behaviour

  18. Feed Characterization • Defined Components (CO2, H2S, C1 to C6 ) • Well Defined using gas chromatography analysis • C7+ Characterisation • Pseudo component approach • Continuous thermodynamics approach • Structured Oriented Lumping approach • Pseudo component approach is well established and normally employed • Continuous approach have been used for solvent deasphalting, but still under development • Not much information available about application of SOL in solvent extraction

  19. Feed Characterization • Solvent extraction studies such as kerosene extraction, lube extraction, solvent deasphalting requires detailed feed analysis such as GC-MS, NMR, Liquid Chromatography apart from physical characteristics. • All of these facilities available at IIP • Identification of pseudo components is a specialised job and have been carried out for number of feedstocks

  20. Phase Equilibria-Prediction • Activity Coefficients Model • NRTL, UNIQUAC etc • Group Contribution Approach (UNIFAC) • Model parameters normally binary and are fitted as function of temperature • Non uniqueness of parameters - same set of data can be represented with different set of parameters • Successfully applied for sulfolane extraction (NRTL), lube extraction (UNIFAC).

  21. Phase Equilibrium Correlation / Prediction • Selection of Thermodynamic Model • For lighter fractions i.e. upto Naphtha Range • NRTL/UNIQUAC • For heavier fractions eg. Kerosene, Diesel, etc. • UNIFAC • Model Parameters • From Experimental Data (Data Reconciliation necessary ) • From Literature (DECHEMA)

  22. DECISION MAKING CHART LLE NRTL - UNIQUAC Kij Y P< 10 bar Wilson - NRTL - UNIQUAC LLE Kij N UNIFAC LLE Non el. UNIFAC Kij Y Polar RS Pol - MHV2 - SAFT P> 10 bar Kij N PSRK - RKSMHV2 Electrolyte Elect- NRTL Real Non Polar RK - PR - SRK - LK > 1 atm Chao S - Greyson Pseudo Vacuum BK10 - Ideal

  23. Simulation of Solvent Extraction Process • Simulation Studies • Inhouseprogrammes • Commercial Softwares • ASPEN/ PRO II • Validation of Simulations • Experimental Data • Industrial Data

  24. Simulation of Solvent Extraction Process • Process Specifications • Feed Rate • Product Quality / Quantity • Operating Temperature / Pressure • Simulation Studies to determine • S/F Ratio • Product Quality / Quantity • Material Balance • Utility Requirements, Optimization

  25. Design of Extractor • Type of extractor • Choice of dispersed phase • Diameter • Height

  26. Extraction Equipment 25 different types of extractors are in commercial use. Reasons for its diversity • Extraction is a widely used separation process and the equipment must suit the individual characteristics of a process. • In-house development by Licensors

  27. Contacting of Phases • Without external energy input • Use of gravitational force • With external energy input • Mechanical energy • Rotation/Pulsation/Reciprocation • Agitation creates & maintains dispersion

  28. Contacting of Phases(contd.) • Stagewise Contacting • Discrete Units/Stages • In each Unit/Stage phase are • Contacted - Mixed - Separated & sent to next unit • Equilibrium or approach to it achieved in each of these stages

  29. Contacting of Phases(Contd.) • Continuous Contacting • Phases separated only at ends • Mass transfer along the full length • Equilibrium not reached at any point

  30. Extractors (Contd.) Extractor Spray Column • Features • Generally 1-2 theo. Stages possible • Low capital • Operating & maintenance cost • Massive continuous phase entrainment • Simple in construction • Application • Food • Chemical Industries

  31. Extractors (Contd.) Sieve Tray • Features • Higher residence time • Less flexibility of opn. • Preferable for dirty services • Low liquid thru’put • Corrosion & foaming services • Application • Petrochemical Industries

  32. P* } h { Z d P P 2 1 Sieve Tray Extractor

  33. Extractors (Contd.) Packed Column • Features • Less no. of theo. Stages • Increased thru’put and mass transfer area • Reduced backmixing • Improved turn-down ratio • Reduced pressure drop • Application • Petrochemical & Chemical Industries

  34. Packed Column • Packed column provide a good future prospects in existing and new applications • Structured packing may find more applications in future • Distributor designs are critical • Rigorous mathematical modelling like CFD can improve design of distributors and other internals

  35. Packed Column with Structured Packings • Structured packings although expensive being used in various services • Offer larger throughput and avoid maldistribution of dispersed phase • Being successfully used in solvent deasphalting application • Attractive in part of the column to enhance coalescence • Clogging due to degraded and corrosive products is possible

  36. Extractors : Mixer Settler • Features • High Stage Efficiency • Wide Solvent Ratios • High Capacity • Good Flexibility • Scale up • Handles Viscous Substances • Application • Petrochemical, Nuclear, Fertilizer & Metallurgical Industries

  37. Extractors RDC • Features • Reasonable Capacity & HETS • Many stages possible • Reasonable Construction Cost • Low Operating & Maintenance Costs • Application • Petrochemical • Metallurgical • Pharma & Fertilizer

  38. Extractors Light liquid Out Heavy liquid In Light liquid In Heavy liquid out baffle tower

  39. Mechanically Agitated Columns • Do not provide consistent performance over wide range of operation • Most of the RDC being used today are NOT operated with Rotor • Due to their high stage efficiencies, these columns are preferred for laboratory studies

  40. Extractors (Contd.) Centrifugal Extractor • Features • Short contacting time • LTD. space required • Handles easily emulsified materials and system with low density difference • Application • Pharmaceutical • Nuclear • Petrochemical

  41. Extractors in Petroleum Industry • Extractor type Applications • RDC BTX, Lubes • Sieve Plate BTX • Packed Column Lubes • Mixer Settler BTX • Baffle Column Deasphalting

  42. Dispersion For effective contacting of phases one phase is dispersed in another Dispersed Phase Continuous Phase

  43. Continuous Phase VS Dispersed Phase Solvent- continuous Feed- continuous

  44. Criteria for Dispersion • Which phase to Disperse ?Disperse the phase • With higher volumetric rate • To increase interfacial area • Which does not preferentially wet the Plate/Packings • To avoid coalescence • With more Viscosity • More Costly • Holdups are generally ~10% • Capital investment less • More Flammable • Solvent Phase • Less coalescence

  45. Dispersed and Continuous Phase

  46. Column DiameterDepends upon variables • Phase flow(v) ratio • Droplet mean diameter • Physical properties, c, d, c, d and  • Agitation energy, if applicable • Geometry of column internals

  47. Column Height Depends on factors in addition considered for Diameter • Equilibrium relationship • Drop size distribution • Hold up and throughput • Mass transfer coefficients • Backmixing • Radial Mixing • Drop breaking & coalescence

  48. Column Diameter Slip Velocity Concept Vslip=Vd/¤+Vc/(1-¤) where, ¤ is hold up Slip velocity correlations Vslip=Vo(1-¤) Vslip= Vo (1-¤)n Vslip= Vo (1-¤)exp(a¤) where, Vo is characteristic velocity(slip velocity extrapolated to ¤=0 )

  49. Column Diameter Flooding ( maximum attainable holdup) dVd/d¤ = 0 and dVc/d¤ = 0

More Related