Membrane Technology Membrane Nomenclature Retentate residue Feed Permeate

Membrane Technology

Membrane Nomenclature Retentate (residue) Feed Permeate Stage Cut = Permeate Flow / Feed Flow

Membrane Barrier Applications • Polymer Pros – Inexpensive – Flexible – Lightweight compared to glass and metal • Polymer Cons – Insufficient barrier properties

Solution-Diffusion Model Upstream pressure pfeed Downstream pressure pperm • JA Component B Wijmans, J. G. , Baker, R. W. Journal of Membrane Science 107, 1 -21, (1995)

Solution Diffusion Mechanism (Permeability = Solubility * Diffusivity) Solute “dissolves” in polymer ( Solubility ) and moves through the polymer chain gaps (Diffusivity). Solute Dense Membrane Film

Pore Diffusion Mechanism Porous Membrane

Solute moves through polymer channels via diffusive jump (Diffusivity) PTMSP

Membrane Polymers

Relative Permeation Rates Through Polysulfone H 2 O, H 2, He, H 2 S Fast CO 2, O 2 Ar, CO, N 2, CH 4 Medium Slow

Permeability – Selectivity Plot (glassy polymer)

Permeability – Selectivity Plot (rubbery polymer)

Experimental Test Unit

Membrane Example O 2 21 mol % N 2 79 mol % P= 1 atm T = 25 C O 2 rich 1 2 Silicone rubber membrane Case 1: a O 2 / N 2 = 3. 2 P O 2 = 500 Barrer = 5 X 10 -8 cm 3 (STP) cm / ( cm 2 sec cm Hg) Case 2: a O 2 / N 2 = 10. 0 P O 2 = 1 Barrer = 1 X 10 -10 cm 3 (STP) cm / ( cm 2 sec cm Hg) Membrane film thickness (L) = 1000 A Find: Downstream concentrations and membrane area required P= 0 atm T = 25 C Q = 100 scfm

Membrane Example Results a = 10. 0 P = 1 Barrer Area = 315, 000 ft 2 O 2 purity = 72 % a = 3. 2 P = 500 Barrers Area = 630 ft 2 O 2 purity = 43 %

Hollow Fiber Membranes

Hollow Fiber Membrane Cross-section Zoom in

Hollow Fiber Membrane Microstructure Outer wall Anisotropic: has pore size gradient

Typical Hollow Fiber Spinning Process Purge valve Steel Mixing Vessel Mass flow controller Nitrogen Cylinder Spinneret Metering Pump AIR GAP Quench Bath Take-up drum Explosion-proof oven

Hollow Fiber Spinning http: //www. fibersource. com/f-tutor/techpag. htm

Membrane Module Designs Retentate (residue) Permeate Tube side feed

Hollow Fiber Module • Hollow fiber form – Bioseparations • Dialysis • Virus removal – Gas separations – Water purification ABOVE: Hollow fiber membrane module used in the hemodialysis process

Hollow Fiber Module

Spiral Wound Module

Module Performance Variables OD ID L Fiber Properties QO 2 Permeance a Selectivity (QO 2/QN 2) L Length N Number ODOuter diameter ID Inner diameter Operating Conditions Pfeed g Feed pressure Pressure ratio (Pshell/Plumen) Co, cross, or counter

Membrane Simulation Retentate Feed Permeate PD 1 R 1 D 2 R 2 C PC 3 R 3 B PB Coker, D. T. , Freeman, B. D. , Fleming, G. K. “Modeling Multi-component Gas Separation Using Hollow-Fiber Membrane Contactors, ” AICh. E J. , 44(6), 1289 (1998). n A PA Rn Fiber Skin

Membrane Simulation Example 1 Calculate the purity of H 2 in the permeate stream of a hydrotreater membrane unit (which separates H 2 from a mixture of CH 4, C 2 H 6, and C 3 H 8 ) as a function of hydrogen recovery in the permeate of two cases: A) B) Feed pressure = 79. 0 bar , permeate pressure = 7. 9 bar Feed pressure = 113. 5 bar, permeate pressure = 42. 4 bar. Data: Feed composition (mol %) H 2 CH 4 C 2 H 6 C 3 H 8 60. 0 22. 0 8. 0 6. 0 4. 0 Permeance (GPU) 100. 00 2. 86 3. 03 2. 00 1. 89 Feedrate = 1000 SCFM, Operating temperature = 60 C, Fiber count = 50, 000

Membrane Simulation Example 2 One option for recovering CO 2 from coal fired power plant flue gas is a multi-stage membrane system. Determine the required area for each stage of the following membrane system. Determine the compressor horsepower requirements of the system. 1. 8 X 106 SCFM total flow of flue gas at 115 F and 16 psia Feed - 13 volume percent CO 2, 87 volume percent N 2 Two stage unit: PF = 500 psia, Pp = 35 psia P CO 2 = 200 GPU, P N 2 = 5 GPU

Nitrogen Separation Applications Oil Well, Pressure Control Inert Atmosphere Military Fuel Tank Protection

Hydrogen Separation Applications Hydrogen removal in refineries, ammonia plants, and olefin units.

Ethylene Plant Application MEMBRANE PERMEATE HYDROGEN Light Hydrocarbons RESIDUE Sieve Dryer Feed FURNACE COOLING Caustic Scrubber LIQUIDS Heavier Hydrocarbons

CO 2 Separation Applications CO 2 removal in natural gas CO 2 removal in synthetic natural gas

CO 2 Recovery - Amine Unit vs Membrane System

Hybrid System Composed of Both an Amine and Membrane System for CO 2 Processing Sales Gas Amine Contactor Membrane Unit Acid Gas Feed Acid Gas Amine Stripper Compressor

Reverse Osmosis Dense Film Liquid Feed PHigh Water Product PLow Water PHigh – PLow > Osmotic Pressure

Concentration Polarization Reverse Osmosis Application Dense Film Liquid Feed PHigh Water Product PLow Water Salt PHigh – PLow > Osmotic Pressure ? ?

Ceramic Membranes