PETpla.net Insider 10 / 2018

MATERIALS / RECYCLING PET planet Insider Vol. 19 No. 10/18 www.petpla.net 11 CarbonLite processes PET fines with Starlinger recycling line PET recycling all-in-one CarbonLite Industries LLC recently installed a recoStar PET 125 HC iV+ bottle-to-bottle recycling line from Austrian manufacturer Starlinger recycling technology at its plant in Dallas, Texas. At this 23,000m² facility with an annual recycling capacity of well above 45,000 t of bottles, CarbonLite recycles not just clear PET bottle flakes, but also more challenging material streams such as coloured material as well as so-called PET fines. PET fines are small particles of 1-3mm in size (bottle flakes have a size of >3mm) that are a by-product of washing and grinding. These fines tend to show higher surface moisture and have a lower intrinsic viscosity (IV) than regular bottle flakes, and they typically contain a larger amount of contami- nants such as paper, glue, metal, or PVC. As a result, many recyclers do not process the fines together with PET bottle flakes, but instead sell them off for use in different applications. The desire to use this waste in a more profitable and sustainable way prompted CarbonLite to investigate recycling options. Starlinger recycling technology offered an all-in-one solution that can operate with PET fines as well as PET bottle flakes, or with a mixture of both. The line consists of the main stages pre-drying, extrusion, degassing, melt filtration, pelletising, crystallisation, and solid-state polycondensation. Due to the special characteristics of PET fines, the steps that require particular attention are melt filtration and decon- tamination as well as IV increase during solid-state polycondensation. Continuous melt filtration with power backflush To extract the high amounts of con- tamination, the recycling of PET fines calls for a melt filter with a large surface area and a special self-cleaning mode. The MPB1940P supplied by Starlinger recycling technology is a continuous melt filter with a unique design for the removal of solid contaminants. Two pistons that carry eight screens provide a total open filter surface of 1,940cm². When the surface of a screen becomes clogged, the backflush function cleans it fully automatically: the contaminants are flushed out through pressure build-up and a reversal of the melt flow. The melt filter is equipped with hydraulic power backflush. The high pressure involved in this auto-cleaning process leads to short backflush cycles and thereby keeps melt loss to a minimum. Unlike conventional backflush filters, the power backflush works with two additional pis- tons that generate extra backflush pres- sure independently of the melt pressure that builds up in front of the pelletising head. Through filtration under constant pressure, a consistent pellet size is achieved during the backflush pro- cess. The lifetime of the filter screens is longer, which lowers operating and maintenance costs. During a screen change, the recycling machine does not have to be stopped, as the remaining screens take over and filter the entire melt stream. IV increase Another important aspect in fines processing is intrinsic viscosity (IV). Due to their higher surface moisture and level of contamination, fines tend to lower the IV of the recycled material; consequently, it has to be raised to the required level. To accomplish this, Car- bonLite operates a Starlinger solid-state polycondensation reactor for high IV increase and superior colour values. Decontamination for direct food contact The cleaning efficiency of the Star- linger PET iV+ recycling process guar- antees the requirements of national and international food safety authorities such as FDA or EFSA. The bottle-to-bottle recycling line from Starlinger recycling technology holds a letter of non-objection by the FDA for 100% rPET – this means that the recycled material is food-safe and can fully replace virgin pellets in the production of PET bottles. The recycling line at the CarbonLite Dallas plant is highly versatile: It can produce rPET for a variety of applications, as the material is suitable for direct food contact with or without treatment in the downstream solid-state polycondensation reactor. The Starlinger recycling line was installed in Dallas in June/July 2018. The installation and start-up posed a challenge insofar as the schedule outlined by the customer was exceptionally tight. „CarbonLite asked us to install the line without interrupting their daily oper- ations, which left us with a short time frame,” says Stefan Obermüller, Head of Project Management at Starlinger. “But only six weeks after delivery of the line, it was already running three shifts and producing material with the agreed specification.” The line achieves a throughput of 950-1,050kg/h and allows CarbonLite to process a maximum of PET waste that it obtains from materials recovery facili- ties. “We initially approached Starlinger for a solution for our PET fines,” states Leon Farahnik, Chairman and CEO of CarbonLite Industries. “But the longer we discussed the project with them, the more Starlinger customised the recycling line, giving us maximum flexibility to process a great variety of input streams into high- end rPET pellets.” www.recycling.starlinger.com