Distillation Column Design Calculation 1u1h2s

Estimating dew point and bubble point using Microsoft Excel From previous chapter, we get Distillate, D= Bottom, B=

95.6103 154.7063

From journal, it says that distillation is not feasible at atmospheric pressure. According to journal also, the system pressure must be under vacuum to make the distillation feasible. So, we take 20 KPa as our system pressure. From Antoines's Equation log P*= A -B/T+C For estimating the dew pint of top distillate. A

B 6.97851 6.2553 7.1345

C 1495.58 912.87 1516.07

P* (in mm Hg) P* (in KPa) 209.559 62.5812556236 8.3434812185 109.13 25.362926672 3.381445454 174.57 14.3459154381 1.9126314234

Using Excel Solver

comp C (LD) D (HD) A

yi

ki αi xi 0.98 0.417174061 2.4674303732 0.9520590206 0.02 0.169072273 1 0.0479416193 0 0.095631571 0.5656253958 0 sigma xi= 1.0000006399

Estimating bubble point for bottom product A

B 6.97851 6.2553 7.1345

C 1495.58 912.87 1516.07

209.559 109.13 174.57

P* (in mm Hg) P* (in KPa) 272.8009274911 36.3704657606 184.2875240158 24.5696491722 95.944008327 12.791482426

Using Excel Solver,

comp C (LB) D (HB)

xi

ki αi 0.012 1.818523288 0.588 1.228482459

yi 1.4803005735 1

0.0218222795 0.7223476857

A

0.4 0.639574121

α LD = α LB =

2.467430373 1.480300574

α, L, avg= Log α, L, avg=

1.911161583

0.5206212891 sigma yi=

0.2558296485 0.9999996136

0.2812974069

To find the minimum number of stages, we use equation 11.7-12 from Transport Processes and Separation Principles Book, Nm

=

log [(X,LD*D/X,HD*D)(X,HW*W/X,LW*W)]/Log α, L, avg

log [(X,LD*D/X,HD*D)(X,HW*W/X,LW*W)] Nm

=

=

12.01924553 minimum number of stages

Using shortcut Method from Transport Processes and Separation Principles Book to find the number of stages at operating Reflux ratio. From journal,

R= R= Rm=

2.18 1.5 Rm 1.4533333333

Using Embar and Maddox empirical correlation, we get R/R+1

=

Rm/ Rm+1

0.685534591 =

0.5923913043

We plot using this value into Erbar- Maddox correlation figure,

We get Nm/ N = So, N = N=

0.59

Nm/ 0.59 20.37160259 theoretical stages

Therefore, the number of theoretical stages that we need to produce 75000Mton/yr of Cyclohexanol is 21stages minus at top dew point of 79.05 C and bottom bubble point of 119.67 C

Trial T ( C) Pt (KPa) 79.0479144344 20

Trial T ( C) Pt (KPa) 119.670709298 20

og α, L, avg 3.3809826

1 Reboiler