Chemical Process Design

More documents

Recommendations

Info

SHORT CUT for DISTILLATION COLUMS SIZING Fenske's equation applies to any two components lk and hk at infinite reflux and is defined by N min , where αij is the geometric mean of the α's at the T of the feed, distillate and the bottoms. ( α ) lk / hk R min is given by Underwood with two equations that must be solved, where q is the liquid fraction in the feed.. Gilliland used an empirical correlation to calculate the final number of stage N from the values calculated through the Fenske and Underwood equations (N min , R, R min ). The procedure use a diagram; one enters with the abscissa value known, and read the ordinate of the corresponding point on the Gilliland curve. The only unknown of the ordinate is the number of stage N. ⎛ x Dlk / x ⎞ Blk log ⎜⎜ x Dhk / x ⎟⎟ Bhk N min = ⎝ ⎠ α lk / hk = D lk / hk F lk / hkα log ( ) 3 / 1 α α B lk / hk 16
SHORT CUT for DISTILLATION COLUMS SIZING Simple and direct correlation for (nearly) ideal systems (Westerberg, 1978) • Determine α lk/hk ; β lk = ξ lk ; β hk = 1- ξ hk • Calculate tray number Ni and reflux ratio Ri from correlations (i= lk, hk): Ni = 12.3 / (α lk/hk -1) 2/3 . (1- β i ) 1/6 Ri = 1.38 / (α lk/hk -1) 0.9 . (1- β i ) 0.1 - Theoretical nº of trays N T = 0.8 max[Ni] + 0.2 min[Ni]; R= 0.8 max[Ri] + 0.2 min[Ri] - Actual nº of trays N = N T /0.8 - For H consider 0.6 m spacing (H=0.6 N); Maximum H=60 m else, 2 columns * Calculate column diameter, D, by internal flowrates and taking into account the vapor fraction of F. Internal flowrates used to sizing condenser, reboiler <strong>Design</strong> column at 80% of linear flooding velocity π D A = 4 2 ⎡ V ⎤ = ⎢ ⎥ ⎢⎣ 0. 8U f ε ρG ⎥⎦ If D> 3m Parallel columns * Calculate heat duties for reboiler and condenser n n k k k V k ∑( µ D + µ L ) ∆H vap = µ dk H Q ∆ cond = HV − H L = ∑ k= 1 D k = 1 * Costing vessel and stack trays (24” spacing) vap U f reb = C sb ⎡ ρ ⎤ L − ρG ⎢ ⎥ ⎣ ρG ⎦ Q = V ∆H k vap 0. 5 ⎛ 20 ⎞ ⎜ ⎟⎠ ⎝ σ 0. 2 17
Page 1 and 2: Chemical Process Design  Subj
Page 3 and 4: 1.- INTRODUCTION Process Alternativ
Page 5 and 6: Cost Estimation Method of Guthrie
Page 7 and 8: An example of Cost Estimation Equip
Page 9 and 10: SHORTCUTS for VESSEL SIZING (Flash
Page 11 and 12: SHORT CUT for REACTORS SIZING First
Page 13 and 14: Heat exchanger: Countercurrent, ste
Page 15: HEAT EXCHANGERS 15
Page 19 and 20: DISTILLATION COLUMNS 19
Page 21 and 22: SHORT CUT for COMPRESSORS (or TURBI
Page 23 and 24: Centrifugal pumps selection guide.
Page 25 and 26: Guthrie Material and Pressure Facto
Page 27 and 28: 3.- COST ESTIMATION OF EQUIPMENT: B
Page 29 and 30: MF: Module Factor, affected by BC,

Chemical Process Design

Create successful ePaper yourself

Delete template?

Save as template?