Hydrocarbon Processing - January 2021 - 33

Special Focus

Sustainability
A. A. KISS, University of Manchester, Manchester, UK;
V. N. MALETA, Maleta Cyclic Distillation LLC, Tallinn, Estonia;
and A. SHEVCHENKO and O. BEDRYK, National University
of Food Technologies, Kiev, Ukraine

Cyclic distillation: A novel enhanced technology
for processing hydrocarbons and derivatives
Distillation is the most widespread separation method in history.1 Despite its simplicity and flexibility, distillation remains a
very energy-inefficient process. Novel distillation concepts based on process intensification (PI) principles can deliver major
advantages in terms of significantly lower
energy use and reduced capital costs while
improving ecological efficiency.
The PI concept has been around since
the mid-20th century, but has received
more attention in the last two decades.
The objective of PI is to design substantially smaller plants while improving their
operational safety, environmental performance and energy efficiency. The Rapid
Advancement in Process Intensification
Deployment (RAPID) Institute, supported by the U.S. Department of Energy, has
placed a spotlight on PI in the U.S. RAPID
aims to target and promote major advances in energy efficiency and productivity in
the process industries.2
With respect to PI, distillation has enjoyed a number of major enhancements
based on process intensification-e.g.,
HiGee distillation, dividing-wall column,
heat-integrated distillation, membrane
distillation and reactive distillation.3
Among these advanced technologies, cyclic distillation stands out as a new challenger in fluid separations due to a different way of contacting the liquid and vapor
phases.4 In contrast to classic operation,
cyclic distillation uses separate phase
movement (SPM) that can be achieved
with specific internals and a periodic
operation mode.5 Cyclic distillation can
also bring new life to old distillation columns by replacing classic internals with
new ones and using a cyclic operation
mode. One operating cycle consists of

two key parts: a vapor flow period (when
the thrust of rising vapor prevents liquid
down flow) followed by a liquid flow period (when the liquid flows down the column, dropping by gravity, first to a lock
chamber and then moving to the tray below). FIG. 1 illustrates this operating cycle.6
From the outside, a cyclic distillation
column looks like a regular tower. However, the cross-section view inside a cyclic
distillation column shows the absence of
downcomers and the presence of different
internals (FIG. 1, left) that allow an efficient
separate-phase movement in practical operation. Recent articles and a mini-review
of cyclic distillation provide more details

about the history of cyclic distillation,
working principle, design and control
methods, benefits and limitations.7-10
Theoretical background. The theory
of the cyclic distillation processes has
been developed over several decades of
engineering. The best established design
algorithms for cyclic distillation columns
include analytical and numerical methods of increased complexity and usability,
developed from 1977-2014.11 FIG. 2 illustrates the modeling of a classic theoretical stage and the operating lines in case of
classic vs. cyclic distillation-where L and
G are the liquid and gas (vapor) flowrates,

FIG. 1. Cross-section of a cyclic distillation column (left). Schematics illustrating the operation
principle of the cyclic distillation system (right): vapor flow period, followed by first and second
half-liquid overflow (tray-sluice-tray below).
Hydrocarbon Processing | JANUARY 2021 33

Hydrocarbon Processing - January 2021

Table of Contents for the Digital Edition of Hydrocarbon Processing - January 2021