Solvent Recovery After Extraction by Energy Efficient Membrane Separation Process

Solvent Recovery After Extraction by Energy Efficient Membrane Separation Process Ken Pennisi Praveen Kosaraju Stuart Nemser Compact Membrane Systems, Inc., Delaware, USA www.compactmembrane.com AIChE Annual Meeting San Francisco, CA, November 3-8, 2008

Applications for Solvent Resistant NF Solvent recovery from vegetable oil extraction Separation of pharmaceutical compounds/intermediates Solvent recovery from neutraceutical extraction (e.g. sterol, vitamins) Solvent recovery from solvent-deasphalting process Solvent recovery from waste motor oil re-refining process Solvent recovery from algae oil extraction Oil extraction from corn distillers dried grain Homogeneous catalyst recovery Solvent decolorization, dye separation November 2013 AIChE Annual Meeting San Francisco 2

Solvent Recovery After Extraction Feed Material Solvent Solvent Extraction Solute/Solvent Mixture Solvent Recycle Solvent Recovery (Distillation or Evaporation) Solute November 2013 AIChE Annual Meeting San Francisco 3

Solvent Recovery by Nanofiltration (NF) NF Process Diagram Retentate (Highly concentrated in solutes) Feed (Solvent- Solute Mixture) Retentate Recycle >200 psi Membrane Device Permeate (Recovered Solvent) Feed Pump Advantages of NF over distillation: Highly energy efficient, no phase change Lower operating temperatures Compact and portable system, easy scale-up/scale-down November 2013 AIChE Annual Meeting San Francisco 4

Membrane SelRo MPF-44 Some Commercial SRNF Membranes Manufacturer 030306 SolSep Starmem 122 Separation Layer MWCO (Da) Poor Stability T max ( C) Koch PDMS 250 DMF, NMP, DMAc 40 Silicone base n-hexane Permeance (lit/m2-hr-bar) Reported incompatible (4) References: (1) High flux nanofiltration membranes for a broad range of organic solvents, ICOM 2011. (2) Performance of Nanofiltration Membranes for Solvent Purification in the Oil Industry, Journal of the American Oil Chemists' Society August 2011, Volume 88, Issue 8, pp 1255-1261. (3) General model for prediction of solvent permeation through organic and inorganic solvent resistant nanofiltration membranes, Journal of Membrane Science 334 (2009) 43 49. (4) B. Van der Bruggen, J. Geens and C. Vandecasteele, Sep. Sci. Technol., 2002, 37, 783. (5) Characterization of organic solvent nanofiltration membranes in multi-component mixtures: Membrane rejection maps and membrane selectivity maps for conceptual process design, Journal of Membrane Science 429 (2013) 103 120. Oil rejection (%) aprotic? 78 (2) UOP Polyimide 220 aprotic, high boiling 50 0.75 (5) 70 (2) DuraMem Evonik Polyimide 150-900 PuraMem Evonik Polyimide 250-480 chlorinated, strong amines polar, polar aprotic; chlorinated; strong amines 50 50 0.58 (5) November 2013 AIChE Annual Meeting San Francisco 5

CMS Perfluoropolymer Based NF Membranes Unique features: Teflon like chemistry and high durability Superior chemical stability High glass transition temperature, superior thermal stability Fouling resistant Higher solvent flux from Higher fractional free volume Ability to make thin film composite membranes Capable of separating/recovering different classes of organic solvents November 2013 AIChE Annual Meeting San Francisco 6

CMS Membrane Chemical Resistance Reagent Temperature ºC Wt % Appearance Change Carbon Tetrachloride 23 0 None 12 N HCl 60 0 None Hexanes 23 0 None MEK 23 0 None 44% NaOH 60 0 None Perclene 23-0.1 None Ethanol 23 0 None Mineral Oil 60 0 None November 2013 AIChE Annual Meeting San Francisco 7

Permeation Properties of CMS NF Membranes Permeance (L/m 2 -hr-b) Solvent Solvent Class At elevated At 25 C temperatures Dichloromethane Halogenated 1.02 Not measured Ethyl Acetate Esters 1.50 Not measured Acetone Ketones 1.15 Not measured MEK Ketones 0.60 Not measured DMF Amide/Aprotic 0.25 Not measured Hexane Aliphatic 3.45 5.8 at 60 C Toluene Aromatic 0.31 0.90 at 68 C THF Ethers/Aprotic 0.36 1.10 at 60 C Dye (Oil Blue, Mol Wt.: 378 Daltons) Rejection: >95 % November 2013 AIChE Annual Meeting San Francisco 8

Hydrocarbon Permeation Rates of CMS NF Membranes Solvent Flux at 150 psi (liter/m 2 -hr) Hexane (C6) 29 Decane (C10) 12 Dodecane (C12) 7 Tetradecane (C14) 4 Hexadecane (C16) 3 Oil Blue Rejection: 93% to 95% November 2013 AIChE Annual Meeting San Francisco 9

Comparison of CMS Membrane to Competitive Membranes Vegetable Oil/Hexane Separation Volume Concentration Ratio (4) Membrane Hexane Permeance (L/m 2 -hr-b) % Oil Rejection 2 CMS 2.18 99+ 2-2 SelRo MPF-50 (1) (PDMS) SelRo MPF-34 (2) (PDMS) SEPA GH (3) (polyamide) 0.18 86 No Permeation 0.46 41-1. Data for MPF-50 from L.P. Raman et al., Fett/Lipid (98), pp.10-14 (1996). MWCO: 700 Daltons 2. Measured in CMS labs. MWCO: 200 Daltons 3. Data for SEPA GH from A.P. Ribeiro et al., Journal of Membrane Science 282 (1-2), pp. 328-336 (2006). MWCO: 1000 Daltons 4. Ratio of the feed volume to the retentate volume November 2013 AIChE Annual Meeting San Francisco 10

Impact of Solute Molecular Weight on Rejection 100 Solute Rejection % 95 90 Pressure = 450 psi 85 350 380 410 440 470 500 Solute MW (g/mol) November 2013 AIChE Annual Meeting San Francisco 11

Impact of Solute Concentration and Pressure on Permeance & Solute Rejection hexane/soybean oil Pressure Normalized Flux (L/m 2 -hr-bar) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 25 50 60 Concentration of Oil (wt%) 450 psi 600 psi 800 psi 450 psi rej. 600 psi rej. 800 psi rej. 100 90 80 70 60 50 40 30 20 10 0 Solute Rejection (%) November 2013 AIChE Annual Meeting San Francisco 12

Impact of Flow Velocity on Permeance hexane/soybean oil 1.6 Pressure Normalized Flux (L/hr m 2 bar) 1.4 1.2 1 0.8 0.6 0.4 0.2 0 Pressure = 600 psi 10 15 20 25 30 Superficial Velocity (cm/s) 0 wt% 25 wt% 50 wt% 60 wt% November 2013 AIChE Annual Meeting San Francisco 13

Change in Permeance Over Time hexane/soybean oil Pressure Normalized Flux (L/(hr m 2 bar)) 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 10 wt% oil Pressure: 450 to 800 psi Temperature: 24 to 32 C 0 50 100 150 200 250 300 Time (hours) November 2013 AIChE Annual Meeting San Francisco 14

Example Application: Separation of n-hexane from Soybean Oil Conventional Separation Process Seeds In Meal Out Refined Oil Out Seed Conditioning Operations Meal Drying and Cooling Oil Refining Operations Crude Oil < 100 ppm Hexane Steam Strip Miscella 2 10 wt% Hexane Solvent Extraction ~60 C Meal Desolventizing Toasting (DT) Miscella 25 35 wt% Hexane Evaporation 1 Evaporation 2 Miscella 70 75 wt% Hexane Vapor Condensers Hexane Key issues associated with solvent recovery by evaporation: Energy intensive - latent heat energy associated with phase change of the solvent Vaporization of hexane increases potential for Fugitive emissions of hexane, categorized by the EPA as hazardous air pollutant (HAP) Fire or explosion November 2013 AIChE Annual Meeting San Francisco 15

Example Application: Separation of n-hexane from Soybean Oil NF Membrane Separation Process Key advantages of solvent recovery by NF: Low energy input no phase change Not a phase equilibrium driven process. Operating temperature is independent of pressure. Temperature can be relatively low or up to 90 C. Easily retrofitted to existing processes November 2013 AIChE Annual Meeting San Francisco 16

Perfluoropolymer NF Process - Greenfield Oil in the Feed or Retentate Loop (wt%) Solvent recovery by the membrane separation process Pressure Normalized Permeance (L/m 2 -hr-b) Oil in the Permeate Stream (wt%) Percentage of Original Solvent Recovered from the Feed 20 1.1 0.018-30.6 0.91 0.027 43.4 45.7 0.63 0.080 70.2 62.8 0.32 0.24 85.2 66 0.26 0.32 87.1 November 2013 AIChE Annual Meeting San Francisco 17

Perfluoropolymer NF Process - Retrofit Membrane separation unit upstream of the evaporators as a first step in solvent recovery: Case-A: For Cost reduction through energy savings Case-B: For plant capacity expansion & to save on energy costs November 2013 AIChE Annual Meeting San Francisco 18

Energy Savings in Retrofit from NF Process (simple analysis) Retentate: 40 units Oil: 25 units, Solvent:15 Units Feed: 100 units Oil: 25 units Solvent: 75 units Membrane Separation Unit Permeate: Solvent: 60 units Existing Evaporators 80% of the original solvent recovered by energy efficient membrane process Recovery of the remaining solvent Energy costs of evaporator = 3 x energy costs of membrane separation process Say, 80% of solvent is recovered by the energy efficient membrane separation process Say, energy costs of evaporator to recover one unit of solvent: $1 Energy costs of evaporator (to recover 75 units of solvent): $75 Energy costs of hybrid process (Membrane + evaporators): $20+$15= $35 Membrane (to recover 60 units of solvent): $60/3= $20 Evaporator (to recover 15 units of solvent): $15 Energy costs savings from the hybrid process (Membrane + evaporator): $75-$35 = $40 (53%) November 2013 AIChE Annual Meeting San Francisco 19

Economics of the NF Process in Solvent Recovery from Vegetable Oil Extraction Greenfield* Retrofit** Percentage cost savings relative to evaporators (%) 49 39 Cost savings per thousand pounds of crude oil processed $1.95 $0.96 Annual cost savings in a plant $361,000 $178,000 Pay back period (years) N/A 2.0 * Greenfield: NF Membrane Process + PV Membrane Process ** Retrofit: NF Membrane Process + Evaporators Basis: Edible oil plant with 22,000 lb/hr of crude oil processing capacity Cost savings of nanofiltration process are relative to evaporation Costs accounted for include all major capital and operating costs. Solvent concentration leaving NF membrane is 25 wt%, estimated optimum final concentration. November 2013 AIChE Annual Meeting San Francisco 20

Summary Because of their unique features, perfluoropolymer NF membranes offer superior: solvent flux chemical & thermal stability fouling resistance range of applicability NF technology is highly energy efficient compared to distillation or evaporation for recovering solvents. Separation by NF does not involve vaporization Minimizes risk of fire or explosion Reduces potential for fugitive emissions Not a phase equilibrium driven process. Operating temperature is independent of pressure. NF technology is easily retrofitted to existing processes. November 2013 AIChE Annual Meeting San Francisco 21

Acknowledgements The authors gratefully acknowledge the support of: The U.S. Department of Energy The National Institute of Health & The U.S Department of Agriculture through Small Business Innovation Research (SBIR) Awards. November 2013 AIChE Annual Meeting San Francisco 22