Unformatted text preview: : Calculation of batch rectification of a ternary mixture with a processsimulation
program.
Given: Charge of 100 kmol of 30 mol% methanol, 30 mol% ethanol, and 40 mol% npropanol
at 120 kPa. Column with the equivalent of 10 theoretical stages, plus a still and a total
condenser. Total reflux condition is established by time zero. UNIFAC method for liquidphase activity coefficients. Column pressure drop is 8 kPa. Condenser pressure drop is 2 kPa.
Two operation steps, each of:
15 hours duration at a distillate flow rate of 2 kmol/h and a reflux ratio of 10.
Assumptions: Negligible holdup in the column and the condenser system.
Find: Molefraction compositions and amounts of each of the 3 products.
Analysis: Use the Batch distillation program of Chemcad to make the calculations. The
flowsheet below includes a batch column (1), a time switch (2), and 2 tanks (3 and 4). The following pages are printouts of the input data and the results of the calculations by the
Chemcad program. This is followed by a summary of the results for the three products. Analysis: (continued)
Process Simulator Input Data: Exercise 13.29 (continued) Analysis: (continued)
ProcessSimulator Results: Exercise 13.29 (continued) Analysis: (continued) Exercise 13.29 (continued) Summary of Results: Cut
Amount, kmol
Mole fractions:
Methanol
Ethanol
nPropanol MethanolRich
30 EthanolRich
30 PropanolRich
40 0.923
0.077
0.000 0.077
0.871
0.052 0.000
0.039
0.961 Exercise 13.30
Subject: Calculation of batch rectification of a ternary mixture with a simulation program.
Given: Charge of 100 kmol of 30 mol% methanol, 30 mol% ethanol, and 40 mol% npropanol
at 120 kPa. Column with the equivalent of 10 theoretical stages, plus a still and a total
condenser. Total reflux condition is established by time zero. UNIFAC method for liquidphase activity coefficients. Column pressure drop is 8 kPa. Condenser pressure drop is 2 kPa.
Three operation steps, each of:
at a distillate flow rate of 2 kmol/h and a reflux ratio of 10.
Duration of the operation steps: Step 1: 13 hours, Step 2: 4 hours, Step 3: 13 hours
Assumptions: Negligible holdup in the column and the condenser system.
Find: Molefraction compositions and amounts of each of the 4 products.
Analysis: Use the Batch distillation program of Chemcad to make the calculations. The
flowsheet below includes a batch column (1), a time switch (2), and 2 tanks (3, 4, and 5). The following pages are printouts of the input data and the results of the calculations by the
Chemcad program. This is followed by a summary of the results for the three products. Analysis: (continued)
Process Simulator Input Data: Exercise 13.30 (continued) Analysis: (continued)
Process Simulator Results: Exercise 13.30 (continued) Exercise 13.30 (continued) Analysis: (continued)
Process Simulator Results: Summary of Results: Product
Amount, kmol
Mole fractions:
Methanol
Ethanol
nPropanol MethanolRich
26 Slop Cut
8 EthanolRich
26 PropanolRich
40 0.960
0.040
0.000 0.518
0.481
0.001 0.035...
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 Spring '11
 Levicky
 The Land

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