CHEMCAD steady-state (https://www.chemstations.com ) is used to simulate the liquid–liquid extraction and distillation
processes used to separate butanol from the fermentation broth. The
UNIFAC LLE model was used to predict thermodynamic parameters, with
all other thermodynamic settings left at the CHEMCAD default values.
Water, mesitylene, and n-butanol are the only components
considered. The flow rate of mesitylene into the extractor relative
to the flow of the fermentation medium is set such that 99% of the
generated n-butanol is extracted. The first distillation
column is defined to remove water such that the remaining weight fraction
is 0.5% of that of butanol, and the second distillation column is
defined to separate the maximum amount of n-butanol
while the mesitylene weight fraction in the product stream remains
less than 0.5% (final butanol purity >99%). The mesitylene from
the
bottom fraction of the second distillation column is then recycled
for further extraction of butanol. Heat exchangers transfer heat from
this hot mesitylene stream to the mesitylene-rich fraction leading
to the distillation columns, recycling some of the heat used in the
separation process (a minimum temperature difference of 10 °C
is assumed). The flow rate of mesitylene, consumption of mesitylene,
product recovery fraction, energy demands of the distillation columns,
and sizes of distillation columns calculated here are then used in
the broader process model and techno-economic analysis.
processes used to separate butanol from the fermentation broth. The
UNIFAC LLE model was used to predict thermodynamic parameters, with
all other thermodynamic settings left at the CHEMCAD default values.
Water, mesitylene, and n-butanol are the only components
considered. The flow rate of mesitylene into the extractor relative
to the flow of the fermentation medium is set such that 99% of the
generated n-butanol is extracted. The first distillation
column is defined to remove water such that the remaining weight fraction
is 0.5% of that of butanol, and the second distillation column is
defined to separate the maximum amount of n-butanol
while the mesitylene weight fraction in the product stream remains
less than 0.5% (final butanol purity >99%). The mesitylene from
the
bottom fraction of the second distillation column is then recycled
for further extraction of butanol. Heat exchangers transfer heat from
this hot mesitylene stream to the mesitylene-rich fraction leading
to the distillation columns, recycling some of the heat used in the
separation process (a minimum temperature difference of 10 °C
is assumed). The flow rate of mesitylene, consumption of mesitylene,
product recovery fraction, energy demands of the distillation columns,
and sizes of distillation columns calculated here are then used in
the broader process model and techno-economic analysis.
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