cpp – Process technology for the chemical industry 01.2019

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SPECIAL
Safe transport of BHET
Filling containers in a
closed nitrogen loop
Conveying and handling are critical steps in any production process. Together with
Ioniqa, Dinnissen has developed a closed-loop pneumatic transport system for BHET,
an intermediate in the production of PET. To solve the problems of product degradation
and particulate matter explosion, nitrogen is used as the transport medium.
Bis(2-Hydroxyethyl) terephthalate
(BHET) is the ester of ethylene glycol and
terephthalic acid. Together with 2-hydroxyethyl
terephthalic acid, BHET is an intermediate
in the production of PET. Ioniqa
manufactures BHET, the raw material for
manufacturing PET products, by chemically
recycling PET flows. The question that arose
was how this product – solid particulate
matter consisting of small pellets as well
as somewhat smaller particles – could be
safely blown by dryers into 20 ft containers
to fill the liner? This question was quickly
answered thanks to Dinnissen’s experience
and expertise. Together with Ioniqa,
Dinnissen developed a closed-loop
pneumatic transport system for BHET.
It is well known that using nitrogen can
eliminate the risk of product degradation
and particulate matter explosion. To solve
the problems, therefore, it was decided to
use nitrogen as the transport medium for
the BHET. The system that has now been
developed monitors the critical oxygen
level continuously. It includes a nitrogen
balancing system which ensures that the
complete system is constantly filled with
the correct nitrogen atmosphere at a
predetermined overpressure.
The entire closed-loop system is enclosed
and in line with Ioniqa’s vision of a circular
economy. Only a minimum amount of
nitrogen is used. Moreover, the system
offers 100 % safety in the event of an electrical
discharge in the liner of the 20 ft
container, because the product is transported
and the liner filled in a completely
inert environment.
Controlled speed of the product flow
An additional advantage of the closed-loop
pneumatic conveying system is that it is
possible to fill the container optimally by
controlling the speed of the product flow.
This volume control is relatively simple to
realise by using a frequency regulator to
adjust the gas volume moved by the blower.
The final point to be considered was gastight
sealing of the transport line to the
liner of the container. It was decided to use
a special, proven clamp adapter with an inflatable
seal. The return gas is fed via this
adapter to a filter unit, then compressed
and cooled before being reused as a carrier
gas.
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Hall 4, Booth 371
Picture: Dinnissen
The closed-loop pneumatic transport system for BHET uses nitrogen as the transport medium
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