A continuous distillation column is operating at steady state to purify alcohol from a mixture of water and alcohol. Addition of salt breaks the azeotrope and allows for more pure alcohol. Liquid containing, by mass, 55% isopropanol, 8% salt and the rest water, is fed to the column. The vapor product stream (distillate) at the top of the column flows at the same mass flow rate as the bottom liquid stream (bottoms). The vapor product stream contains 80% isopropanol and no salt.a. Define azeotrope and explain why adding salt allows removal of more water from alcohol.b. Draw and label a flowchart. Do degree of freedom analysis to see if all unknowns can be solved.c. Calculate the mass fraction of salt in the bottoms.d. Calculate the fraction of isopropanol from the feed that is in the bottoms (kg IPA in bottoms/kg IPA in feed).
A continuous distillation column is operating at steady state to purify alcohol from a mixture of water and alcohol. Addition of salt breaks the azeotrope and allows for more pure alcohol. Liquid containing, by mass, 55% isopropanol, 8% salt and the rest water, is fed to the column. The vapor product stream (distillate) at the top of the column flows at the same mass flow rate as the bottom liquid stream (bottoms). The vapor product stream contains 80% isopropanol and no salt.
a. Define azeotrope and explain why adding salt allows removal of more water from alcohol.
b. Draw and label a flowchart. Do degree of freedom analysis to see if all unknowns can be solved.
c. Calculate the mass fraction of salt in the bottoms.
d. Calculate the fraction of isopropanol from the feed that is in the bottoms (kg IPA in bottoms/kg IPA in feed).
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