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 gas-tight 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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