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The plant supplied to Closed Loop
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When Closed Loop Recycling began producing food contact grade HDPE from transparent bottle material back in 2008, the recycler used B+B Anlagenbau and Erema for the design and build of the line. The group, which is in a phase of expansion, has now ordered the third of these systems – with a capacity of 7,000 tonnes per year. This takes the existing plant capacity to 4,800 kg/h in total.
The process at Closed Loop involves dry cleaning, air classification, hot wash, sink float separation and mechanical drying from B+B, with subsequent extrusion and upstream decontamination from Erema. This recycler is producing rHDPE pellets from HDPE milk bottles for direct food contact in line with EFSA standards.
The basic principle of B+B’s plant concept is to treat the regrind material in a dry state as long as possible while it is in the process. This means that water and other resources can be saved, and no elaborate plant engineering is required for processing.
The core component of the washing facility is the hot wash, which removes unwanted elements such as stickers or adhesives from the regrind material. Crucial to the cleaning process is the removal of milk residues and the associated odours. To support this, the hot wash system works continuously and is fully automatic, keeping maintenance intervals at a minimum.
During extrusion, the food contact grade HDPE regrind is produced on two Vacurema Advanced 1716 TE systems. The regrind is then reused in the production of milk bottles.
With a market share of 50% in the USA and 30% in Europe, Vacurema technology from Erema is well-known. Erema claims that the key to its success in such applications is decontamination upstream of the extrusion process. The patented pre-treatment of the HDPE flakes, at raised temperature and in high vacuum before the extrusion process, removes moisture and migration materials from the feedstock in a stable process environment.
The parameters for direct food contact compliance are monitored and archived continuously in the recycling process on all Vacurema systems. The Food Contact Control (FCC) feature supervises the recipe data stored and if levels go beyond defined limits an alarm is triggered automatically and (optionally) material flow is diverted away from current production.
Higher-quality washing processes have posted significant growth in recent years as the cold wash used previously for the processing of polyolefins was not able to completely remove strong odours, says Erema. This can limit applications to outdoor use items.
In the USA, polyolefin repellets are already being used in the washing detergent and cosmetics industries. B+B has commissioned several hot wash systems for such projects in recent times, with annual capacity in the region of 90,000 tonnes globally.
Of course, for Erema, recycled PET is a massive market. Approximately 295,000 tonnes of waste PET in the US are processed to make rPET for direct food contact — half of which is processed using Vacurema. All in all the group states that there are more than 150 Vacurema systems in use around the world, producing high-quality repellets and end products such as films, with an overall annual capacity of around 1 million tonnes.
The vacuum treatment means that stable IV values can be achieved even if moisture levels vary. Input materials with up to 1.5% moisture can be processed, which can mean that additional pre-drying equipment is unnecessary. Extruder degassing is not required either, meaning that a short extruder screw can be used and the thermal stress on the material is reduced as a result. The Austrian recycling specialist claims that its patented configuration is comparitively low-maintenance.
The repellets/end products produced with Vacurema technology for direct food contact fulfil the purity requirements of many major brand owners and is certified by the FDA and EFSA (see figure 1 in the image slider above). “Some 347,000 tonnes of rPET for direct food contact are produced every year with Vacurema systems. And in doing so, our customers use up to 100% of the recycled pellets for the production of bottles and food contact grade thermoforming sheet in accordance with efsa guidelines,” said Christoph Wöss, Vacurema Product Manager.
Erema says that an independent testing institute has confirmed that Vacurema technology has “the best energy efficiency ratings compared to others” (see figure 2 in the slider). A total of eight different PET recycling technologies available on the market were tested for electrical and thermal performance. The Vacurema Inline Sheet system (used to produce food contact grade thermoforming sheet) of a customer in Germany came out on top in an energy comparison with other systems available on the market, recording the lowest specific total energy consumption (including sheet downstream) of 0.29 kWh/kg.
Vacurema also reportedly proved to be 40% more energy efficient than other systems in the bottle-to-bottle field with a rating of 0.295 kWh/kg. This is due in part to the decontamination process before extrusion which requires only a single energy input for processing.
The very large active filter areas of the Erema filter systems also contribute to efficiency performance. The patented partial surface backflush screen changers from the RTF series feature a fully automatic self-cleaning system which, despite extremely fine filtration (32 µm screen mesh), allows low pressure losses, high filter capacity and long filter service life, according to the group, resulting in highly clean repellets.
Erema's high-performance filters, which can be connected directly to the extruder outlet, are often used for large area ultrafine melt filtration in the production of flat film, with some film plants now using the Erema piston screen changer as standard. These are available in a variety of sizes and output levels, up to a six-piston system with twelve parallel filter screens.