Page 319 - Pressure Swing Adsorption
P. 319

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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