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The process appears to run correctly through all its stages: crystallization and pre-drying, extrusion, pelletizing and post-crystallization.
The pellets coming out of the centrifuge are white and glossy, have a homogeneous IV value and are ready for the final step of IV-boosting and decontamination (super-clean).
They are then reheated and fed into the Solid State Polycondensation (SSP) tower - under nitrogen atmosphere or under vacuum with nitrogen flow.
🟥 But here a problem arises: 𝘁𝗵𝗲 𝗽𝗲𝗹𝗹𝗲𝘁𝘀 𝗲𝘅𝗶𝘁𝗶𝗻𝗴 𝘁𝗵𝗲 𝗿𝗲𝗮𝗰𝘁𝗼𝗿 𝗮𝗿𝗲 𝘃𝗶𝘀𝗶𝗯𝗹𝘆 𝘆𝗲𝗹𝗹𝗼𝘄𝗲𝗱.
The heat required for the polycondensation reaction has triggered a 𝘁𝗵𝗲𝗿𝗺𝗮𝗹 𝗱𝗲𝗴𝗿𝗮𝗱𝗮𝘁𝗶𝗼𝗻 that did not appear in the previous stages.
Pellets that were formally suitable up to that point suddenly become 𝗻𝗼𝗻-𝗰𝗼𝗺𝗽𝗹𝗶𝗮𝗻𝘁 𝗳𝗼𝗿 𝗳𝗼𝗼𝗱-𝗰𝗼𝗻𝘁𝗮𝗰𝘁 𝗮𝗽𝗽𝗹𝗶𝗰𝗮𝘁𝗶𝗼𝗻𝘀: they may be downgraded and sold for alternative uses (e.g., strapping) or reprocessed, but they can no longer be used in food-grade applications.
The result is the 𝗹𝗼𝘀𝘀 𝗼𝗳 𝘁𝗼𝗻𝘀 𝗼𝗳 𝗺𝗮𝘁𝗲𝗿𝗶𝗮𝗹, 𝘄𝗮𝘀𝘁𝗲𝗱 𝗸𝗪𝗵 𝗼𝗳 𝗲𝗻𝗲𝗿𝗴𝘆, 𝗻𝗶𝘁𝗿𝗼𝗴𝗲𝗻 𝗮𝗻𝗱 𝗼𝘁𝗵𝗲𝗿 𝗼𝗽𝗲𝗿𝗮𝘁𝗶𝗼𝗻𝗮𝗹 𝗰𝗼𝘀𝘁𝘀 - all inevitably thrown away.
💡 𝗧𝗵𝗶𝘀 𝘀𝗰𝗲𝗻𝗮𝗿𝗶𝗼 𝗰𝗮𝗻 𝗼𝗰𝗰𝘂𝗿 𝗶𝗻 𝗿𝗣𝗘𝗧 𝗯𝗼𝘁𝘁𝗹𝗲-𝘁𝗼-𝗯𝗼𝘁𝘁𝗹𝗲 𝗽𝗹𝗮𝗻𝘁𝘀 𝘄𝗵𝗲𝗿𝗲 𝘁𝗵𝗲 𝗦𝗦𝗣 𝗿𝗲𝗮𝗰𝘁𝗼𝗿 𝗶𝘀 𝗽𝗼𝘀𝗶𝘁𝗶𝗼𝗻𝗲𝗱 𝗮𝘁 𝘁𝗵𝗲 𝗲𝗻𝗱 𝗼𝗳 𝘁𝗵𝗲 𝗹𝗶𝗻𝗲 – 𝗮𝗳𝘁𝗲𝗿 𝗲𝘅𝘁𝗿𝘂𝘀𝗶𝗼𝗻 𝗮𝗻𝗱 𝗽𝗲𝗹𝗹𝗲𝘁𝗶𝘇𝗶𝗻𝗴.
At that stage, the only corrective action is to over-dose the melt with anti-yellow additives - even when, in reality, they would not be needed.
🟩 The 𝘀𝘁𝗿𝗮𝘁𝗲𝗴𝗶𝗰 𝗰𝗼𝗻𝗳𝗶𝗴𝘂𝗿𝗮𝘁𝗶𝗼𝗻 of the 𝗶𝗤𝗼𝗻𝗶𝗰𝗧𝘄𝗶𝗻 𝗛𝘆𝗽𝗲𝗿𝗣𝗘𝗧 stands in sharp contrast to competing mechanical-recycling systems, because 𝘁𝗵𝗲 𝗦𝗼𝗹𝗶𝗱 𝗦𝘁𝗮𝘁𝗲 𝗣𝗼𝗹𝘆𝗰𝗼𝗻𝗱𝗲𝗻𝘀𝗮𝘁𝗶𝗼𝗻 (𝗦𝗦𝗣) 𝘀𝘁𝗮𝗴𝗲 𝗶𝘀 𝗽𝗲𝗿𝗳𝗼𝗿𝗺𝗲𝗱 𝗯𝗲𝗳𝗼𝗿𝗲 𝗲𝘅𝘁𝗿𝘂𝘀𝗶𝗼𝗻.
This approach delivers at least three decisive advantages:
✅ Color correction can be applied to the pellets only when needed and in the exact required amount.
✅ Pellets with non-conforming color are identified 𝘣𝘦𝘧𝘰𝘳𝘦 entering the so-called “food” storage area and can therefore be immediately diverted to the “non-food” zone, preventing contamination.
✅ Production can be stopped instantly if the incoming material shows abnormal levels of non-conformity, avoiding tons of already-extruded waste.
📌𝗖𝗼𝗹𝗼𝗿 𝗰𝗼𝗻𝘁𝗿𝗼𝗹 𝗮𝗻𝗱 𝘄𝗮𝘀𝘁𝗲 𝗽𝗿𝗲𝘃𝗲𝗻𝘁𝗶𝗼𝗻 are only some of the benefits enabled by the strategic configuration of the 𝗶𝗤𝗼𝗻𝗶𝗰𝗧𝘄𝗶𝗻 𝗛𝘆𝗽𝗲𝗿𝗣𝗘𝗧 by MAS Austria.
source : Christian Schiavolin
#PETrecycling
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