Hydrocarbon Processing - January 2021 - 37

Sustainability
tion for multi-component separations.6
An interesting phenomenon that also
occurs in a DWC is the evaporation of
superheated liquid when the steam supply to the column is shut off. This results
in added process efficiency, especially
when obtaining highly pure substances, as
volatiles are the first to evaporate. During
the vapor period, the liquid gathers much
energy; however, when the vapor flow is
stopped, the pressure drops and the superheated liquid boils throughout the DWC.
Modern cyclic distillation technology
works in stripping columns, rectification
columns and tray DWCs with a diameter
range of 400 mm-1,700 mm. Cyclic distillation technology has been used in the
production of ethanol for biofuels and
food, in the recovery of methanol from
water and/or acetone, in the distillation
of various chemicals (ethers, propylene,
propanol, hexane, formalin, aniline, cyclohexane, butyl acetate, ethylbenzene,
methyl acetate, BTX), in isopropyl alcohol dehydration, in industrial solvents distillation (white spirit), in the cleaning of
raw coal benzole, and in the fractionation
of kerosene, with several implementations
in Ukraine, Belarus and Saudi Arabia.
For example, since 2006, one company
has built and installed commercial-scale
plants with cyclic distillation columns of
5-42 trays and column diameters of 0.4
m-1.7 m. In 2014, the same company
built an industrial-scale DWC using cyclic
operation (42 trays, 1.5 m/1.7 m diameter, and a capacity of 25 m3/hr) for a plant
processing kerosene and white spirit.
Promising industrial use. Some
promising areas for using cyclic distillation include the production of high-purity substances, such as:
1. Organic synthesis (e.g., ethyl
acetate, methyl acetate) in reactive
distillation systems, which offers
the ability to control the reaction
on a tray, along with the added
bonus of avoiding erosion of the
solid catalyst due to fluid overflow.
2. Ecological applications (e.g.,
recovery of solvents and
refrigerants and CO2 absorption
processes). A pilot industrial unit
was built in Finland by Eco Scandic
Oy. An additional pilot unit is
planned to conduct research on the
development of new technologies.
Typically, refrigerants are collected
for regeneration by their type

and not as mixtures; however,
in practice there are no ideal
conditions. Mixtures of different
types of refrigerants may be
present in one tank; fractionation
is required to separate and
purify them for further reuse.
Eco Scandic Oy invested in
building a distillation unit for
the fractionation of refrigerants
(as illustrated in FIG. 11). This is a
great prospect for countries with

hot climates and heavy use of
refrigerants, as it can significantly
reduce the environmental burden.
In addition, this unit can be used
for research purposes, since the
unit was designed for pressures up
to 30 bar and deep vacuum.
3. Separations of close boiling
components (such as isomers of
hydrocarbons or isotopes of water).
FIG. 12 illustrates the first use of cyclic distillation DWCs for fractionating kerosene.6

FIG. 9. Quantitative effect of applying cyclic distillation instead of classic distillation to ethanolwater mixtures.

FIG. 10. Cyclic distillation (dividing-wall) columns with coaxial partition-any geometric shape
is possible.
Hydrocarbon Processing | JANUARY 2021 37

Hydrocarbon Processing - January 2021

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