L5 - Lecture 5: Distillation Two modes: 1) Continuous or...

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Lecture 5: Distillation Two modes: 1) Continuous or steady state 2) Batch Steady state flash distillation Q Furnace Vapor F moles yD for A distillate (1-f) moles xB of A Bottoms Separator Feed xF mole fraction of component A F = 1 moles f: fraction vaporized depends on heat input Q
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Material balance on A: xF= f*yD + (1-f)*xB yD = [-(1-f)/f]*xB + xF/f @State line with slope = -(1-f)/f @Pass thru ( xF,xF) yD (xB=xF) = -(1-f)xF/f +xF/f = xF[1-1+f] = xF xB,yd are in thermodynamic equilibrium , yD = ye(xB) yD xB xF (xF,xF) Operating line Equilibrium line x y f=0
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Steps: 1) Draw equilibrium curve 2) Find (xF,xF) on the diagonal line 3) Calculate slope of operating line = -(1-f)/f where f is the fraction vaporized. 4) Draw a line with slope –(1-f)/f. 5) Find intersection with equilibrium curve, (xB,yD) 6) Calculate T from (T-xy) diagram. AB C xB xF yD (y,T) (x,T) T (x,y) T operating
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Remarks: @ As f increases, abs(slope) = (1-f)/f decreaseas. @ For f = 0, slope = -(1-f)/f = -inf xB = xF, yD = ye(xF) @ For f = 1, slope = 0 yD = xF, xF = ye(xB) @ For 0<f< 1, f = AB/AC(Lever Rule) @ As f increase, yD decreases, xB decreases, T increases x y xB yD (xF,xF) f=1 f=0
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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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L5 - Lecture 5: Distillation Two modes: 1) Continuous or...

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