Solvent Recovery After Extraction by Energy Efficient Membrane Separation Process

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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

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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

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Solvent Recovery After Extraction

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Solvent Extraction Solvent Recovery (Distillation or Evaporation) Feed Material Solvent Solute/Solvent Mixture Solute Solvent Recycle

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Solvent Recovery by Nanofiltration (NF)

Advantages of NF over distillation:



Highly energy efficient, no phase change



Lower operating temperatures



Compact and portable system, easy scale-up/scale-down

Membrane Device Retentate Recycle Permeate (Recovered Solvent) Feed (Solvent-Solute Mixture) Feed Pump Retentate

(Highly concentrated in solutes)

>200 psi

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Some Commercial SRNF Membranes

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.

Membrane Manufacturer Separation Layer

MWCO

(Da) Poor Stability

T max (°C) n-Hexane Permeance (lit/m2-hr-bar) Oil rejection (%) SelRo MPF-44 Koch PDMS 250 DMF, NMP, DMAc 40 Reported incompatible(4) 030306 SolSep Silicone base aprotic ? 78 (2) Starmem

122 UOP Polyimide 220 aprotic, high boiling 50 0.75

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DuraMem Evonik Polyimide 150-900 chlorinated, strong

amines 50

PuraMem Evonik Polyimide 250-480

polar, polar aprotic; chlorinated; strong

amines

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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

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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

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Permeation Properties of CMS NF Membranes

Solvent Solvent Class

Permeance (L/m2_-hr-b)

At 25°C At elevated 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 %

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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

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Comparison of CMS Membrane to Competitive Membranes

Vegetable Oil/Hexane Separation

Volume Concentration Ratio(4) Membrane Hexane Permeance (L/m2_-hr-b) % Oil Rejection 2 CMS 2.18 99+ 2 SelRo MPF-50(1) (PDMS) 0.18 86 - SelRo MPF-34 (2) (PDMS) No Permeation -2 SEPA GH (3) (polyamide) 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

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Impact of Solute Molecular Weight on Rejection

85 90 95 100 350 380 410 440 470 500

Solute Rejection %

Solute MW (g/mol)

Pressure = 450 psi

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Impact of Solute Concentration and Pressure

on Permeance & Solute Rejection

hexane/soybean oil

0 10 20 30 40 50 60 70 80 90 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 25 50 60 Solute R e jec tion (% ) Pressure Normaliz ed Flux (L/m 2 -hr-bar) Concentration of Oil (wt%)

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Impact of Flow Velocity on Permeance

hexane/soybean oil

November 2013 AIChE Annual Meeting ‐San Francisco 13 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 10 15 20 25 30 Pr ess u re Normaliz ed Flux (L/hr ‐ m 2 ‐ba r) Superficial Velocity (cm/s) 0 wt% 25 wt% 50 wt% 60 wt% Pressure = 600 psi

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Change in Permeance Over Time

hexane/soybean oil

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 50 100 150 200 250 300 Pr essur e Normaliz ed Flu x (L /(hr ‐ m 2 ‐ba r) ) Time (hours) 10 wt% oil Pressure: 450 to 800 psi Temperature: 24° to 32° C

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Example Application: Separation of n-Hexane

from Soybean Oil

Conventional Separation Process

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 Seed Conditioning Operations Solvent Extraction ~60° C Desolventizing Toasting (DT) Meal Drying and Cooling Evaporation 1 Evaporation 2 Steam Strip Seeds In Miscella 70 – 75 wt% Hexane Meal Crude Oil < 100 ppm Hexane Oil Refining Operations

Refined Oil Out

Miscella 25 – 35 wt% Hexane Miscella 2 – 10 wt% Hexane Vapor Condensers Hexane Meal Out

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Example Application: Separation of n-Hexane

from Soybean Oil

NF Membrane Separation Process

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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.

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Perfluoropolymer NF Process - Greenfield

Solvent recovery by the membrane separation process Oil in the Feed

or Retentate Loop (wt%) Pressure Normalized Permeance (L/m2_-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

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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

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Energy Savings in Retrofit from NF Process

(simple analysis)

• 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%) Membrane

Separation Unit Existing Evaporators

80% of the original solvent recovered by energy efficient membrane process

Recovery of the remaining solvent Feed: 100 units Oil: 25 units Solvent: 75 units Retentate: 40 units

Oil: 25 units, Solvent:15 Units

Permeate: Solvent: 60 units

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Economics of the NF Process in Solvent

Recovery from Vegetable Oil Extraction

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.

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