1 / 35

Rigorous Simulation of Divided-wall Columns

Rigorous Simulation of Divided-wall Columns. M. Shamsuzzoha, Maryam Ghadrdan, Ivar J. Halvorsen, Sigurd Skogestad The 15th NPCW'09, Telemark University College, Porsgrunn, Norway January 29-30 2009. Trondheim, Norway. NTNU/SINTEF Trondheim. A. B. ABCD. C. D.

fabian
Télécharger la présentation

Rigorous Simulation of Divided-wall Columns

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. Rigorous Simulation of Divided-wall Columns M. Shamsuzzoha, Maryam Ghadrdan, Ivar J. Halvorsen, Sigurd Skogestad The 15th NPCW'09, Telemark University College, Porsgrunn, Norway January 29-30 2009

  2. Trondheim, Norway

  3. NTNU/SINTEF Trondheim

  4. A B ABCD C D Minimum Energy for the Four-Product Kaibel Distillation Column Introduction What is Petlyuk columns Experimental setup Assessment by the Vmin diagram Rigorous simulation Summary

  5. 3-product Petlyuk arrangement A AB ABC B BC C A AB B ABCD C CD D BEEDIST (Basic Energy Efficient Distillation Technology) NTNU lab • Founded by the Norwegian Research Council through the GASSMAKS program • SINTEF/NTNU 2008-2012 • Objectives • Study new integrated distillation arrangements • For reduction of capital cost and energy consumption (+ CO2-emission related to the energy). • 20-40% savings in reach. • Evaluate application in natural gas processing and conversion. • Design and operation • Develop laboratory • 2 PhD + post doc 4-product Kaibel-column with a dividing wall

  6. A ABC B C What is a Petlyuk arrengement ? • Integrated distillation column arrangement • Separates a single feed into three separate products • Just a single reboiler and condenser Why? • Saves energy and capital • Distillation consumes 3-5% of the industry energy consumption world-wide=>Need more energy efficient solutions

  7. Industrial DWC/Petlyuk applications German-speaking community dominates • BASF: 40 DWCs in operation. Increasing. G. Kaibel pioner • Monz – main vendor for BASF • Krupp-Uhde • Sulzer • Rashig • Linde Others • MW Kellogg (UK) • UOP (USA) • UK, Japan, Indonesia, South Africa The Kaibel-column 4-product DWC!

  8. A A AB AB Liquid split ABC ABC B B Vapor split BC BC C C Equivalent Petlyuk arrangements Dividing Wall Column (DWC) Classical Petlyuk arrangement Fully thermally coupled sections

  9. A A B ABC ABC AB BC B C C Conventional alternatives for 3-product separation: Sequence of binary columns Indirect split: IS Direct Split: DS

  10. Prefractionator arrangement Alternatives for 3-product separation... A AB ABC B The prefractionator does the simple A/C split while B distributes to both ends B BD C

  11. Conventional Prefractionator arrangementwith a single main column A AB ABC B BC C

  12. Apply full thermal coupling A Petlyuk column AB ABC B BC C

  13. Why consider a Petlyuk arrangement • Large potential energy savings compared to conventional columns (20-30%) • Or – increase production for given energy supply • Capital cost savings due to more compact equipment => smaller footprint and removal of reboiler/condenser units • Usage: • In theory: Anywhere (almost) where distillation is a suitable separation technology and more than 2 products are produced. • In practice: Some cases may be unsuitable due to required temperature/pressure range, height, or if liquid/vapor load in different sections are very different. • Practical variations can be made, e.g. side-strippers/rectifiers • Revamping of existing conventional columns may have significant potential

  14. Critical: How to set the splits • The potential savings are easily lost unless the splits are adjusted properly • Do it right and obtain all the benefits! liquid split (side draw) A liquid split (Rl) D1 A ABC ABC B B V1 vapor split (Rv) vapor split (side draw) C C

  15. A AB B ABCD C CD D Extend to 4-product DWC:The Kaibel column – (1987) Separates 4 products in a single shell! Total reflux section Can save 30-40 %

  16. Minimum energy-Definitions and assumptions • Vapour flow rate (V) generated from all reboilers is used as the energy measure • Ideal Assumptions • Infinite number of stages • Constant relative volatility • Constant molar flow • Constant pressure • No internal heat exchange • Then, exact analytic solution is obtained

  17. Minimum energy (Vapor flow rate V) • Sharp splits: Flat optimum at a line segment (optimality region) • Optimality region depends on feed properties • Rapid increased vapor flow outside optimality region

  18. V/F D/F 1 The Vmin-diagram Operation point f(D/F,V/F) Distillate (D) Binary column –multicomponent feed Feed (F) ABC Vapor rate (V) Feed comp. distribution ? Minimum energy ? Two degrees of freedom – choose D/F,V/F

  19. The Vmin-diagram – 3 component example V/F D F ABC Vminboundary V Preferred A/C split D/F

  20. Characterisitcs of operation

  21. A B ABCD C D Schematic diagram of the experimental setup of 4-product Kaibel-arrangement

  22. Lab installation: Height: 8 meters Atmospheric pressure Vacuum glass sections 4 products Contact: Sigurd Skogestad, or Ivar J. Halvorsen A AB B ABCD C CD D The Kaibel column at NTNU, Trondheim, Norway A B Feed (ABCD) C D

  23. Feed condition for the Kaibel Distillation • Four components: Methanol+Ethanol+1-Propanol+1-Butanol • Flow rate F=1.0 Kgmole/h, q=1 (saturated liquid) • Composition z=[0.25, 0.25, 0.25, 0.25] • EOS Wilson • Pressure Atmospheric • Relative volatility α= [8.27: 4.84: 2.30: 1.0]

  24. UniSim Simulation for Kaibel Column

  25. Steady-State Simulation for Kaibel Column KAIBEL DISTILLATION COLUMN

  26. Minimum Energy – competition

  27. Vmin-diagram for the Kaibel column

  28. Vmin-diagram for the Kaibel column using UniSim • Rigorous calculation confirms ideal shortcut method V/F D/F

  29. A AB B ABCD C CD D Further work • Status: Startup of new PhDs • Directions: • Further studies with Unisim (extended from ideal mixtures) • Further development of Matlab models • Alternative structures like HIDiC, Heat integrated and other energy efficient arrangements • Dynamic studies • Optimizing control • Lab column experiments

  30. How to apply DWC/Petlyuk columns • Make sure to do a reasonable design in terms of placement of the dividing wall/design split. • Important: Make sure to indentify the optimality region for the expected actual feed variations, and thereby clarify the requirements for on-line adjustment of: • None of the split ratios (E.g. in case of quadrangle shaped reg.) • Just the liquid split (In case of a line segment reg.) • Both split ratios (in case of a very short line segment) • Determine the final control strategy based the actual product value/energy cost, and dynamic controllability analysis.

  31. Key issues for full thermal coupling • Liquid and vapour flows in equilibrium avoids irreversible loss due to mixing (Petlyuk 1965) => • Explains why Petlyuk columns beat the other arrangements • Require operation of every internal column at its “preferred split” • Underwood roots “carry over” the coupling (Halvorsen 2001) => • Valid for any operating point • Simple sequential calculation sequence • Extremely simple assessment for n-product Petlyuk arrangement based only on feed properties.

More Related