Chemical Engineering May 2010 - 17

Distillation-tray downcomer design
improves mass transfer efficiency
new approach to the design of the
downcomer portion of distillation
column trays - presented at the recent
American Institute of Chemical Engineers
(AIChE) Spring 2010 meeting (San
Antonio, Tex.; March 21-25) - promotes
a uniform fluid flow pattern, which improves
mass transfer efficiency.
The Downcomer Distributor was developed
through a joint research program
between AMT International Inc.
(Plano, Tex.; www.amtintl.com) and Petronas
(Kuala Lumpur, Malaysia; www.
petronas.com.my) with an objective to
eliminate deviations from an ideal fluidflow
pattern that occur on typical distillation
trays, which result from recycling
of fluid on the tray and by the existence
of stagnant regions of liquid.
The Downcomer Distributor technology
results in directional flow and distribution
within the downcomer itself
and as the liquid exits the downcomer.
A
Inside the AMT Downcomer Distributor
(diagram), liquid is distributed according
to pre-determined proportions
by " uniquely arranged, slanted and
triangle-shaped discharge ports " that
initiate and maintain a uniform plugflow
pattern.
In testing, the Downcomer Distributor
consistently resulted in approximately
5-10% greater tray efficiency
compared to existing downcomer configurations
under normal tray operating
conditions and with the same active
valve tray. AMT says that combining
the Downcomer Distributor technology
with its high-performance Advanced
Dispersion Valve (ADV) Trays has demonstrated
efficiency increases of 24%
and 29%, respectively, for liquefied petroleum
gas (LPG) and depropanizer
columns of a large-scale commercial
gas plant.
In addition to increasing masstransfer
efficiency, the elimination of
stagnant zones of liquid on the trays
extends the column runtime, since stagnant
zones tend to foul in dirty service,
says the manufacturer.
The Downcomer Distributor technology
has been applied at several commercial
distillation columns, starting in 2008,
including at several Petronas plants.
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Chemical Engineering May 2010

Table of Contents for the Digital Edition of Chemical Engineering May 2010
