This
paper introduces multiple esterification reactions of three
alcohols occurring in a single reactive distillation (RD) column and
reports significant energy savings by combining three reactions in
the single unit. To realize a feasible integration of the three reactions,
the removal of the common water product from the unstable heterogeneous
azeotrope should be possible through liquid–liquid decantation
in the eight-component system. For this multireaction system, only
the direct sequence can produce three esters with a purity higher
than 99.0 mol % due to the behavior of liquid–liquid phase
equilibrium. We demonstrate an economic evaluation of the direct sequence
of a single RD column simultaneously producing the three esters by
comparing the direct sequence with the two parallel RD sequences in
the same design basis. The total annual cost of the triple esterification
direct sequence is reduced by 21.3–25.2% compared to that of
the parallel esterification system.
This
study introduces a pinch-based method to design an internally
heat-integrated pressure swing distillation (HIPSD) with a double
annular column. In the configuration, the annular stripping section
of a low-pressure (LP) column partially wraps around the rectifying
section of an inner high-pressure (HP) column to minimize exergy loss.
In order to enable adequate heat transfer and azeotropic separation,
the key factor is setting the pressure of the columns by considering
the so-called pinch pressure, which is determined by the minimum temperature
approach and circumvention of the azeotropic boundary. This heat integration
between two individual columns reflects different overall heat transfer
coefficients for each stage, because they are affected by the composition
of the fluid and its hydrodynamic characteristics. Each column is
also sized to meet hydraulic conditions to ensure separation efficiency.
The HIPSD of several azeotropic mixtures was described and the maximum
energy savings reached 23.80%.
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