Page 320 - Pressure Swing Adsorption
P. 320

ii  I
  t       MEMBRANE PROCESSES
 PRESSURE SWING ADSORPTION
 296                                                                   297
  I
 Dense Non-Porous
 Active Laver
 1000A
 j_   I

 T   l



 Porous Sublayer
 ~0.2mm
 I
 J_





 Permeate Gas
 Figure 8.5  Schemauc diagram solving construct100 of an asymmetric membrane.











 Permeate




                                        (c)
                                 Figure 8.6  (Contmued).
 (bi
          t1on  to  the  separation  (Figure  8.5).  The  two  most  common  types  of mem-
          brane module are shown  rn  Figure 8.6.  J n  the  hollow fiber  module  the  fibers
 Hollow,
 thin-walled   are connected between ''tube plates",  as  rn  ,1  .shell  and  tuhc  heat  exchanger,
 porous tubes   but  the  fiber  bundle  IS  often  twisted  to  promote  radial  mixing  on  the  shell
          side. There 1s  some disagreement as  to  the  best  flow  direction, and commer-
          cial  systems  are  available  with  both  inward  and  outward  flow.  From  the
          process standpoint outward  flow  1s  preferable, smce  1t  1s  easier to mamtam a
 Retentate
          good  approx1mat10n  to  plug flow  on  the  high-pressure  side  if  the  high-pres-
          sure  flow  goes  through  the  tubes  rather  than  through  the  shell.  This.
 Figure  8.6  Membrane  modules:  (a)  soiral  wound,  (b)  hollow  fiber  type,  and
 .. lc)-~yw·"al  "'ll?u-sr·•le ••nit-- (Cnur1~sy.0f now~Generon  In.c.)
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