EQUILIBRIUM STAGED SEPARATIONS o Single Stage Flash/Flash Drum ◆ Distillation E Simple distillation E Complex distillation E Non-deal distillation o Gas Absorption and Stripping Liquid-Liquid Extraction ◆ Multi-Effect evaporation 0/6/99 Equilibrium Staged separations
0/6/99 Equilibrium Staged Separations 1 EQUILIBRIUM STAGED SEPARATIONS u Single Stage Flash [Flash Drum] u Distillation ð Simple Distillation ð Complex Distillation ð Non-Ideal Distillation u Gas Absorption and Stripping u Liquid-Liquid Extraction u Multi-Effect Evaporation
PHASE EQUILIBRIUM Q Conditions for thermodynamic equilibrium between two phases f=,i=1,…,ne TO= TO) and P()=P(2) For an ideal system fA(=yi P and L=x; Pi(T 0/6/99 Equilibrium Staged separations
0/6/99 Equilibrium Staged Separations 2 PHASE EQUILIBRIUM uConditions for thermodynamic equilibrium between two phases f i *(1) = fi *(2) , i = 1,…,nc T(1) = T(2) and P(1) = P(2) u For an ideal system f i *(V) = yi P and fi *(L) = xi Pi S (T)
PHASE EQUILIBRIUM DEFINITIONS K-value Ki=y/A For an ideal system K=Pi()/P o Relative Volatility ak of component with respect to component k a n=K Kk 0/6/99 Equilibrium Staged separations
0/6/99 Equilibrium Staged Separations 3 PHASE EQUILIBRIUM DEFINITIONS u K-value Ki Ki = yi /xi For an ideal system Ki = Pi S (T)/ P u Relative Volatility ajk of component j with respect to component k ajk = Kj / Kk
FLASH DRUM VAPOR Yi EED Zi iting Or Cooli g OUD 0/6/99 Equilibrium Staged separations
0/6/99 Equilibrium Staged Separations 4 VAPOR V Yi LIQUID L Xi Heating Q or Cooling FEED F Zi FLASH DRUM
FLASH DRUM PERFORMANCE ◆ Separation Factor SF ∥ Detween components I dk SF ik= SR, SRk But SR VY/lX and sR k VY/LX So sFik =/vY; /LX /Yk/lx=K /k=aik ◆ Conclusion The maximum separation is limited by the relative volatility aik which is set by nature Fractional Recovery of component FR=/F;=两y+Lx/=/SS+1 where S V.L 0/6/99 Equilibrium Staged separations 5
0/6/99 Equilibrium Staged Separations 5 FLASH DRUM PERFORMANCE u Separation Factor SFjk between components j and k SF jk = SRj / SRk But SRj = V Yj / L Xj and SRk = V Yk / L Xk So SF jk = [V Yj / L Xj ] / [V Yk / L Xk ] = Kj / Kk = ajk u Conclusion The maximum separation is limited by the relative volatility ajk which is set by nature. u Fractional Recovery of component j FRj = Vyj / F zj = Vyj / [Vyj + L xj ] = [ Sj / Sj + 1] where Sj = VKj / L