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The Buhler Group has developed a comprehensive and economical technology for the continuos upgrading of post consumer PET bottle flakes into new pellets suitable for direct food contact. This new PET recycling process fits well into the Bühler scope since Buhler Group have been successful on the market for many years with Solid-State Polycondensation (SSP) plants for virgin PET where Buhler have installed more than 75 plants with single line capacities of up to 450 tpd representing a world wide market share of  57%.

The increased consumer awareness for PET recycling has lead several companies to include the recycling aspect into there marketing strategy. With Buhler experience and with the many years of close cooperation with most of the key players in the virgin PET Industry, it was almost a natural step for Bühler to react to the demand for an economical PET recycling process.

In this newly designed Buhler Bottle-to-Bottle recycling process, the washed PET flakes are dried, melt-decontaminated and then pelletized. Then the decontaminated pellets are crystallized and solid stated and finally cooled in a continuous Buhler 3-step SSP process. In this Buhler solid state polycondensation process the pellets are upgraded to properties and qualities comparable to virgin materials.

Recycling of post consumer PET bottles into reusable bottle grade PET chips, can be separated in 4 major subjects:

1.    Collection of post consumer PET bottles
There is the need for a collection system of post consumer bottles. A good quality of collected bottles will make reclaiming much easier and opens up the potential for reduced investments in the reclaiming area. Most important is, however, to have a constant quantity of post consumer bottles.

2.    Reclaiming includes washing – size reduction - sorting
In a second step, the post consumer bottles need to be washed, sorted and flaked. The washing is repeatedly done in different steps and serves the purpose of cleaning the surface from impurities and to wash of labels and glue. The size reduction from the post-consumer bottle to the flakes is done in a cutter. The size reduction to flake size of approximately 10-12 mm and not more than approximately 3 mm thickness is a common size. The sorting process separates other plastics and polymer foreign materials from PET and also sorts different colours such as clear, green, blue and others.

The quality of PET flakes resulting from this reclaiming process is a pre-determining factor for the final quality of the recycled PET material. Non-PET impurities or inefficient colour sorting will damage the material quality non-reversible once the material has gone through the melt-phase in the extruder.

The equipment needed for the reclaiming as describe above is not part of the Buhler scope of supply.

Buhler is in a position to either recommend suitable companies to work with or find ways of a cooperation between Buhler and third companies in order to act as full scope supplier.

The washed and sorted flakes are processed in a Buhler Bottle-to-Bottle system to re-produce PET pellets suitable for direct contact with food again.

3. Drying, melt-decontamination, melt-filtration and pelleting
   In the Buhler Ring-Extruder the PET flakes are dried, decontaminated. The molten mass is then passed through a melt-pump, melt-filter and a die to a pelletizer system. The use of unique Buhler Ring-Extruder eliminates a separate drying unit prior to the extruder and with this reduces energy consumption and investment cost.
   
4. Crystallization, Solid-Stating and Cooling
   After the extrusion the pellets need to be crystallized again and then solid-stated. For this a new designed continuous 3-step Buhler SSP system is available. After this Buhler solid-state polycondensation process the recycled PET is of a comparable quality to virgin PET bottle material and is suitable to be reused for manufacturing articles intended for use in contact with all types of food under conditions C (including hot filled and pasteurised above 150°F (65°C)) and less severe conditions. This has been confirmed by the American Food & Drug Administration with the FDA “Non-Objection-Letter” we received for this Bottle-to-Bottle process.

 For today’s industrial applications recycling plants are planed for capacities between 1200 kg/hr (30 tpd) or 2400 kg/h (60 tpd). The first Buhler Bottle-to-Bottle system sold in Europe (30 tpd) is presently under construction and will start commercial production in fall of this year.

Larger capacities than 60 tpd can be built, however, the availability of post consumer PET bottles are often the limiting factor. For smaller capacities such as 600 kg/h, the economy of scale needs to be observed carefully since reduction of capacity and reduction of investment are not in line.

The chart below shows some of the key values calculated for a Buhler Bottle-to-Bottle upgrading process based on Swiss production cost:

For the above “Upgrading Cost from flakes to Pellets” cost factors included are:

•    Depreciation of plant over a period of 5 years

•    Interest rates of 7% paid for Buhler scope of supply incl. installation.

•    Cost for insurance 2.5 %

•    Cost for maintenance and repairs

•    Cost for labour (production and maintenance)

•    Cost for all types of energy

•    Cost for loss of material (-weight-loss due to drying etc) ca. 1.25%.

•    Cost for leas of building

The values used for investments of the Bottle-to-Bottle system include equipment beginning with the feeder for the cleaned flakes into the extruder and ends with the cooler for upgraded PET bottle grade pellets.

Not included in the Buhler scope of supply are:

• Cost for land (size depending on material storage concept)

• Cost for utility generation systems (electric power, nitrogen and water)

•  Cost for utility piping

•  Cost for building and infrastructure

•  Storage area for flakes and pellets

•  Cost for erection, start-up of system

•  Cost for training of production and maintenance engineers.

For the mechanical and electrical system erection of the Bottle-to-Bottle plant, for the start-up and for training of operator and maintenance engineers Buhler  estimate 12'000 Men-hours, assuming that most of the labor could be contracted from local companies. Buhler would then delegate one mechanical and one electrical supervisor for the duration of the erection. For the start-up and for training of operator and maintenance engineers a Buhler software and a process engineer are included in the above approximation of the 12'000 men-hours.

Bühler AG

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Edited: 12.03.2002