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The urgency for Crystallisers in China
Crystallisers Engineering Escher Process Modules Technology

Growing economy

The Chinese economy is still growing rapidly and the need for raw materials is great. Shenhong Refinery Petrochemical Corporation in Lianyungang, Eastern China, has ordered 24 Crystallisers from Escher Process Modules, a subsidiary of Iv-Groep. Para-xylene, the raw material for the manufacture of PET bottles, will later no longer need to be imported. The Chinese client wishes to have the installations ready by September 2020. This will put construction under a huge amount of (much needed) pressure.

Scraping crystals

The Crystallisers will be part of a new, gigantic petrochemical complex in China. How it works: The Crystalliser tank is filled to the brim with 250,000 litres of xylene, with some residues of toluene and benzene which is covered by a ‘blanket’ of nitrogen to ensure toxic vapours cannot escape. Ethylene, a gas that varies in temperature (between -35 and -84 degrees Celsius) during the process and cools the contents of the tank, is introduced through the double wall on the underside of the tank and approximately halfway up. Para-xylene crystallises at a temperature of 13 degrees above zero. A layer of crystals form on the inner wall of the tank and are removed by revolving scrapers. The crystals then sink to the bottom, where a sort of slush puppy forms. The liquid and the ice are discharged via the underside. At the same time, new liquid is fed via the topside of the tank to maintain a constant level. The ice is separated from the liquid in three stages via a centrifuge. Each stage increases the purity of the product. Eventually, para-xylene is produced. Once the installation is underway, it will run continuously, month in, month out.

‘Installed base’

Escher has been active in process technology since 1925 and has built up an excellent reputation. Already in 1998, five Crystallisers of this type were delivered to BP in Geel, Belgium. The Crystallisers have been running successfully there for the past twenty years. This is an ‘installed base’ and is very important for scoring follow-up assignments. Our strength is that we have many kinds of divisions within Iv-Groep, each possessing specific expertise. These divisions all work in close collaboration for the Crystallisers. “Additionally, we found the best suppliers for the construction of the Crystallisers. They are also our partners because we needed more from this collaboration. The pressing of time due to the tight deadline is enormous. Every project brings challenges," laughs Hugo Keemink, Technical Coordinator of the project.

Reversed engineering

Escher was already supplying Crystallisers twenty years ago, but because there are no longer personnel within the organisation who previously worked on this, the new Crystallisers must be designed based on the old data. Moreover, the specifications have intensified. We have travelled several times to China to first, convince the customer that Escher's solution was the best and safest option. And especially, to take on board the wishes of the customer.
One of the requirements is an extra safety feature, a torque limiter, developed for the gearbox and with planetary gears in three stages. In the exceptional case that the motor jams or a tooth breaks off a sprocket , the liquid will take the rotor with it and the forces will become ten times greater than the forces delivered by the motor. Should this happen, the torque limiter will intervene and disconnect the rotor from the motor.
Compared to the old design, further improvements have been made, such as a dry gas mechanical seal and a direct drive mechanism . The construction is calculated at the higher speed at which this installation will run at 20 revolutions per minute, compared to 11 revolutions with the former design.

The extensive article can be found in our magazine.

Would you like to know more about this project? Fedor will be pleased to share ideas with you about this matter. Contact him via 088 943 3300 or send an email.
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