The growth in consumption of polyphenylene sulfide (PPS, an engineering
plastic primarily used in electronic component manufacture) has fueled the
demand for high-purity para-dichlorobenzene (p-DCB). The smallest amount of
impurities in the starting monomer can significantly affect the quality of the
final product. Purification can be established by e.g. distillation, however
the close boiling points of the main impurities ortho- and meta dichlorobenzene
requires a large number of trays
Suspension based melt crystallization is
an attractive alternative for purification of isomers like e.g.
para-dichlorobenzene (p-DCB). The energy of crystallization for p-DCB is close
to a factor 3 lower than the heat of evaporation, facilitating significant
energy savings.
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techsheet
Compared to the batch wise operated static or dynamic
layer crystallization, the suspension based melt crystallization process
features continuous operation at also significant lower energy consumption.
Crystal growth rates are over a factor 1000 lower, ensuring gentle formation of
ultra pure crystals.
As a solid liquid separator, GEA
Messo P.T. applies washcolumns which can efficiently separate the pure
crystals from the mother liquor. In the wash column, the pure crystals are
rigorously washed with their own melt, eliminating the use and related recovery
of a separate wash liquid. A wash column has low operating speeds which results
in a proven long lifetime of the moving parts.