Chapter 4 REACTOR DESIGN FOR MULTIPLE REACTIONS Single reactions +  + − =      Because of • high   and − • small   PFR  BR Single reactions Conversion Multiple reactions Selection Conversion Parallel reactions            −  =      −  =      = −  −  =             >  Because of • high   and  • small   • and are contravariant   <  Because of • low   • high  • and are covariant PFR   CSTR  BR =           1−     Parallel reactions  +     +     −  =          −  =          = −  −  =                    >    >  Because of • high   ,  and  • small      >    <  Because of • low   • high   and  PFR    BR  Semi BR   Semi PFR   =               1−       −        Parallel reactions  +     +     −  =          −  =          = −  −  =                    <    <  Because of • low   ,  • high     <    >  Because of • low   • high   and  Semi BR   Semi PFR     CSTR =               1−       −        Series reactions          −  =      −  =      = −  −  =             Because of • high   and   • high  • and are contravariant PFR  BR Complex reactions                    −  =      −  =       −  =         >  Because parallel and series reactions are also require the BR and PFR   <  PFR  BR Semi PFR  PFR  PFR  CSTR PFR  CSTR Polymerization reactions Polymerized by functional groups Polymerized by free radical Polymer has a narrow distribution of molar mass because of the same residence time Polymer has a wide distribution of molar mass because the monomer and free radical concentrations decline Polymer has a wide distribution of molar mass because of different residence time Polymer has a narrow distribution of molar mass because the monomer and free radical concentrations are maintained PFR  BR  CSTR PFR  BR  CSTR Biochemical reactions Promoted by microorganisms Promoted by enzymes   +    −  =       +  The reaction rate is the same to the autocatalytic reactions, reactor depends on   −  =       +  Because of high   ,  PFR  CSTR PFR  BR  CSTR PFR  CSTR Conclusion of multiple reactions If and are contravariant: • ≈50%in irreversible reactions • ≈50%  in reversible reactions If and are covariant: • ≈95%in irreversible reactions • ≈95%  in reversible reactions [...]...Single reversible reactions The effect of feed ratio on equilibrium conversion Single reversible reactions The effect of inert material on equilibrium conversion Parallel reactions + + − − = = = Semi BR − > − Excess Semi PFR Semi BR − < − Excess Semi PFR Parallel reactions + + ∆ < + + = − − = − Concentrations of inert... Series reactions − − = = BR + PFR − = − Semi BR Semi PFR = = Because of • low and high = Excess because of • low • high and Removal • low Series reactions − − = = CSTR = − PFR − Removal • low • shift equilibrium Concentration of inert and are covariant ∆ < Concentration of inert and are contravariant ∆ > Recycling undesired Use one reactant in excess for parallel reactions. .. reactions Maximize = − − + > < − − , use excess , use excess + + Decrease concentration of inert Increase concentration of inert Reactor Separator Reactor Product Separator + + Reactor Separator + Feed + Product Change Mixing characteristics Temperature Pressure Catalyst Product +