L23 - 4/27/2004 1 embrane Seperation Processes. A + B More...

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Unformatted text preview: 4/27/2004 1 embrane Seperation Processes. A + B More A, less B Less A, more B 4/27/2004 2 Ex Gases: Air- O 2 ,N 2 Liquids A + Water -- water with less salt + salty Two kinds of Membranes:-Porous Membranes : Diffusion-Polymeric Membranes : Sublimation + Diffusion Seperation of Gases through a porous membrane: Pores are narrow, r = radius of pore r<1um Knudsen Diffusion, = mean free path of any molecule >r For O 2 around room T and P , 1000A~1um- Knudsen diffusivity D A = 9700* r *(T/M)^0.5 where r = pore radius Bigger molecules diffuse faster D e,A = D A * / , = porosity, = tortuosity. L L 4/27/2004 3 J A = D e,A C A ./ z = D e,A P A / zRT Assumed C A = P A /RT ; Ideal Gas J B = D e,B P/ zRT Say steady state diffusion Composition of the Permeate, y Az = J A / J A + J B = P A /M A ^0.5/( P A /M A ^0.5+ P B /M B ^0.5 Example PA1 = PB1 = 1atm (P1 = 2atm, x A = 0.5) PA2 = 0.6atm PB2= 0.4 atm implies P CA1, PA1 CA2,PA2...
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This note was uploaded on 04/15/2008 for the course CHEE 3462 taught by Professor Mohanty during the Spring '07 term at University of Houston.

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L23 - 4/27/2004 1 embrane Seperation Processes. A + B More...

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