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Aspen Separation Unit Operations

Aspen Separation Unit Operations Team 2: Futoon O. Aljirafi, Peter Ho, Neha Kalla, Won Kim, Alexandra Shubina, Rachel Stanoyevitch. Outline. Introduction.

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Aspen Separation Unit Operations

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  1. Aspen Separation Unit Operations Team 2: Futoon O. Aljirafi, Peter Ho, Neha Kalla, Won Kim, Alexandra Shubina, Rachel Stanoyevitch

  2. Outline

  3. Introduction

  4. “A separation process is method to achieve any mass transfer phenomenon that converts a mixture of substances (i.e. chemicals) into two or more distinct product mixtures” 1 There are three different classes of separators found in Aspen: Separators Columns (distillation, strippers, absorbers) Solid Separator The unit operation chosen will depend on the type mixture/solution 8 General Overview

  5. The following selections can be found in Aspen in the Model Palette bar Separators: Columns: Solid Separators: Available Unit Operations

  6. Separators

  7. Flash2 • Single stage separator • Dependent on components’ volatility • Inputs: T, P, Heat duty, or Molar vapor fraction • Selection of property method • SRK/UNIFAC: azeotrope • IDEAL: no azeotrope • Ensure flash convergence (global flash options) • Useful for more complex simulations

  8. Decanter2 • Suitable for a liquid-liquid extraction • Separates based on centrifugation • NRTL method should be used because it is better suited for LLE • If any stream were to have a vapor phase then Flash separator is better suited

  9. Sep/Sep22 • Combine feed streams and create a split depending on user specifications • Useful when details of separation are unknown • Can be used to model flash columns temporarily to make flowsheet work • Sep is good when fractions are known but energy balance is unknown • Sep2 can add specifications like purity and recovery

  10. Columns

  11. Feed purification • Natural gas (desulphurization < 1 ppmv) • Water (impurities ppbv) • Reforming (reformer furnace) • Heated by burning natural gas • Methane + Steam → Hydrogen + Carbon Dioxide + Carbon Monoxide • Methanol Synthesis • Gas compressed and sent into synthesis reactor • Produced methanol separated into crude product: • Methanol (~70%) • Water (~30%) • Traces of byproducts • Methanol purification • Distillation Columns Methanol Synthesis Process: Via Natural Gas Feed3

  12. Shortcut Distillations2 • DSTWU4 • Designed for single feed, two product distillation processes • Use the Winn, Underwood, Gilliland methods to calculate the Nmin, Rmin, and reflux ratio given a number of theoretical stages (and vice versa). Must specify reflux ratio, condenser type, condenser and reboiler pressure, and light and heavy key recovery • Assumes constant relative volatilities and constant molar overflows • Distl4 • Multicomponent distillation model that separates one inlet streaminto two outlet streams. Uses the Edmister methodto calculate column compositions for a given number of stages and reflux ratio • Must specify number of theoretical stages, reflux ratio and distillate to feed ratio (works under the same assumptions as the DSTWU column) • Estimatescondenser and reboiler duties

  13. Rigorous Distillations2 • RadFrac4 • Suitable for all types of multistage vapor-liquid separations • Capable of simulating the following operations: • Absorption, reboiled absorption, stripping, reboiled stripping, azeotropic distillation, and extractive distillation • Can model columns with occuring various chemical reaction types: • Equilibrium, rate, electrolytic • MultiFrac4 • Models complex configurations including: • Any # of columns with multiple stages per column • Random connections within columns and between columns • Random flow splitting and mixing • Typical applications include: • Heat-integrated columns, stripper/absorber, air separation

  14. ConSep and Extract Columns2 • ConSep • Used prior to rigorous simulation using RadFrac • Used for vapor-liquid/vapor-liquid-liquid mixtures • Must specify: reflux or reboil ratio, and column pressure • Extract • Used for liquid-liquid extractions • Accepts specifications for component or stage efficiencies • May include: • Multiple feeds, heater/cooler, side-streams • Must calculate distribution coefficient using the following: • Activity coeff. Model, equation of state, and temperature dependent polynomial

  15. Troubleshoot • Issue: Cost of cooling utility • Use a partial condenser instead of a total condenser in distillation column • Example: • Want to separate water (bottoms) and vinyl acetate (distillate) from a mixture of water, ethylene, nitrogen, carbon dioxide, acetic acid, and vinyl acetate • Add a partial condenser to minimize the cooling utility cost associated with a total condenser (nitrogen released as vapor)

  16. Troubleshoot

  17. Absorption & Stripping

  18. Absorbers and Strippers • Absorber • Separation unit used to dissolve solute into solvent by means of direct contact • Objective is to purify a gas component • Stripper • Separation unit used to remove solute from solvent by means of direct contact • Objective is to purify a liquid component

  19. Customization

  20. Troubleshoot • Increase mass flow rate of liquid if bottom flow rate is zero or increase mass flow rate of gas if distillate flow rate is zero • Decrease number of stages

  21. Solid Separators

  22. Liquid-Solid6 Catalyst recovery: Catalyst from wax product Solid-Solid7 Coal screening: Suitable feed of fine coal ash Solid Separation in Methanol Synthesis: Gas-Solid5 Coal gasification: • Left over ash removed from gaseous products Co-Absorption: • CO and H2 from coke powder

  23. Gas-Solid Separators2 • ESP: dry electrostatic precipitators • Fabric Filter (FabFl): baghouse fabric filter units • Gas Cyclone (Cyclone): centrifugal force of a gas vortex • Scrubber (VScrub): venturi scrubbers, direct contact with an atomized liquid stream

  24. Liquid-Solid Separators2 • Hydro Cyclone (HyCyc): centrifugal force of a liquid vortex • Centrifuge (CFuge): centrifugal force of a rotating basket • Liquid Filter (Filter): continuous rotary vacuum filters • Swash (SWash): entrained liquid of a solids stream • CCD: counter-current decanter or multistage washer

  25. Solid-Solid Separators2 • Screen: separation of various sizes of solid particles in a mixture

  26. Questions?

  27. Work Cited Separation process. http://research.omicsgroup.org/index.php/Separation_process (accessed Feb 5, 2019). AspenTech. AspenPlus User Guide Volume 2. http://www.chemengr.ucsb.edu/~ceweb/courses/che184b/aspenplus/UserGuideVol1.pdf (accessed Feb 5, 2019). Methanol Manufacturing Process. http://www.southernchemical.com/wp/products/methanol/manufacturing-process (accessed Feb 5, 2019). Overney, R. Aspen Tutorial #6: Aspen Distillation. https://courses.washington.edu/overney/Aspen/Aspen_Tutorial_Unit_6.pdf (accessed Feb 5, 2019). Wang, T.; Wang, J.; Jin, Y. Slurry Reactors for Gas-to-Liquid Processes: A Review. Ind. Eng. Chem. Res.2007, No. 46, 5824–5847. Eastland, D. Methanol from Coal; Davy Powergas Inc: Houston, TX. Lewitt, M. Opportunities for Fine Coal Utilisation. IEA Clean Coal Centre August 2011. Distillation Equipments - Distillation Column Manufacturer from Mumbai. https://www.indiamart.com/kalina-engineering-mumbai/distillation-equipments.html (accessed Feb 5, 2019).

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