PET Conventional Recycling Plant (Grinding, Separating, Washing and Drying)

 

Watch Video for a simplified plant  

The description of the system follows the above design.

The system is designed for the production of technically clean PET-Flakes. It comprises the separation of the PET flakes from PO and subsequently also from PVC. Optionally a hot washing system is provides, in case the bottles have LDPE or paper labels that are fixed with a glue that is not dissolvable in water.

 

Production Parameters:                                                        

 

Grinding and Washing Plant:

About 900 - 1000 kg/h  PET-bottles

 Cleanness of PET-Flakes:

 

Technically clean, dependent on water treatment. Suitable for sale or further processing.

 

 

Budget (for the complete configuration incl. options. Clients are free to purchase individual components for their own process): about  € 1,900,000.- ex works Italy

    

Description of the process and the principal components

 

Loading of  the Material

 

The material arrives in bales and is thrown into a pit (civil works). There the bales are opened manually by a helper who removes the binding wires. The bales loosen up due to internal elastic tension.  Then the material is shoved onto the loading conveyor (Pos.1). Normally a mechanical Bale-opener or a Guillotine is not necessary, but can be provided as an option.

 

 

 

Dissolving of the Bales and removal of coarse contamination such as stones, small Fe-metal scraps etc.

 

The material is conveyed (Pos. 2) to a Sieve-Trommel (Pos. 3) where the bottles get separated and coarse contamination is removed. Subsequently the bottles  are discharged to a conveyor (Pos. 4) and pass under a Fe-Separator(pos. 5) . This is necessary to protect the grinder (Pos. 6)

 

Grinding in 2 steps (Vendor items)

In order to bring the flakes to the size of about 8 – 10 mm two grinders are provided. The first with a grid of 50 mm, the second with a grid of 10 mm. The first Grinder (Pos.6) with grid 50 mm is loaded by the mounting conveyor (Pos.4). The flakes are conveyed by a Pneumatic Transport System (Pos. 7) to the second grinder (Pos. 8) with grid size 10 mm  grinds the bottles to a flake - size of 8 – 10  mm.

Subsequently the material passes, via another Pneumatic Transport (Pos. 9) To a Dosage Auger (Pos. 10) for intermediate storage ahead of the Washing Machine ML  (Pos.12) (Option) which by action of hot water and additives, such as Soda or others, removes the glue and the labels of the bottles.

 

Hot Washing and removal of glues and labels from the bottles  (Option)

 

 

 

The Washing Machine ML 1400 (Pos.12) combines the hot washing and removal of the glue and the attached pieces of labels from the surface of the flakes. The patented principle of the system is derived from the mechanical design of the Costarelli densifier, and combines the shredding effect of the rotor blades and the washing caused by injected water and the mutual friction of the plastic particles. Tangentially injected air avoids that the plastic particles stick to the side walls of the drum. In this case the material is already ground so the rotor is used to move the material and generate friction between the blade carrier and the bottom plate of the machine.

The process is batch-wise. The material is loaded from the top and after the washing cycle discharged through a laterally located hydraulically operated flap.

The washing water is discharged through the bottom of the drum. A sieve separates the material from the residues of the washing process. The water can be recirculated before it has to be treated in a simplified water recirculation- and treatment plant.

 

Deep washing and rinsing of the Flakes by action of the Turbowash

 

To obtain the very low degree of impurities required for PET flakes a deep washing process by two Turbowash machines (Pos. 18 and 19) is provided. For a maximum cleanness of the flakes the Turbowash flushes and rinses the flakes with a great quantity of water and subjects them again to the impact of rotating blades.  The design principle of the Turbowash corresponds to a horizontal centrifuge.

 

Dosage Auger for Turbowash

Turbowash

Two Turbowash's in Operation

                Rotor with Blades and replaceable Wear-Plates

 

The Turbowash is specially designed for ruggedness and high reliability. The rinsing - washing effect is caused by the introduction of important quantities of water and the high centrifugal acceleration (600 U/min), the impact of the flakes on the blades and the mutual friction of the rotating plastic-flakes. Simultaneously paper and cellulose is rubbed off the flakes. A special ejection blade provides for high throughput / production, the angle of incidence of the blades provides fort he longitudinal transport of the flakes. The washing water flows into the water circuit via a duct on the bottom of the Turbowash.

 

 

Separation of PET- flakes form PE / PP

 

 

Subsequently a drained auger (Pos.20) conveys the material to the Float-Sink tank (Pos.22). Due to their specific weight >1 the PET sinks, whereas PE/PP, labels and taps float and are removed. These taps and labels have a high commercial value. Because they have passed through the ML 1400 and the Turbowashs they are already cleaned. For efficient separation the material is fed into the tank below the surface.

 

 

Hydrocyclone for separation of PET from PVC (Option, Vendor item)

 

To separate the remaining PVC from PET a Hydrocyclone (Pos. 27) is necessary, because both PET and PVC sink to the bottom of the tank due to their specific weight > 1. The PVC passes through a vibration sieve (Pos. 28) and is discarded.It has to be determined how many Hydrocyclones are necessary in order to reduce the PVC content to 1 ppm.

 

Hydrocyclone

Vibration sieve

 

 

 

Drying of the Flakes

 

After passing through another sieve Trommel (Pos. 29) the flakes are dried to about 1 -2 % in the

Dynamic Drying Centrifuge 850/10 (Friction- Centrifuge) (Pos. 31)

 

The Dynamic Drying Centrifuge is a horizontal centrifuge which combines cleaning and drying of the material.

 

The centrifuge 850/10 is specially designed for ruggedness (Weight of rotor ca.2 t, total weight ca. 4.5 t) and high reliability. The cleaning and drying effect is due to the high centrifugal acceleration (1200 RPM), the impact of the flakes on the blades and the mutual friction of the rotating material.

 

 

 

Centrifuge with pneumatic Transport

Rotor with wear plates

 

The centrifuge is provided with a slowly counter rotating sieve basket. The impact of the material and the water droplets on the sieve basket causes a self-cleaning effect of the basket.

 

The residual humidity depends on the thickness of the flakes.

 

  

Storage and BigBag Loading for Sale

 

 

After the drying the flakes are conveyed by a pneumatic transport to the Mixer Silo (Pos. 34) and then to the Storage Silo (Pos.35) from which the can be filled into BigBags for shipping.

 

Project - Parameters:

 

 

The space requirement is about 750 m2 (without storage space). This can be optimized together with the buyer during the detailed planning phase. A simple prefabricated building and a concrete slab foundation is sufficient canals for electric cables and water has to be foreseen.

 

Operation Parameters:

 

The plant can be operated automatically via a PLC (not included) according to the buyer’s requirements.

 

Personnel Requirements (4 Turn-Operations):

 

1 Turn-Supervisor with tradesman’s education

1 Fork-lift truck driver

1 Helper

 

Personnel not in Turn:

 

1 Manager

1 Secretary

1 Electrician

1 Mechanic

 

Energy Requirement:

 

Installed Power about 830 kW

Energy consumption (2/3 Installed Power) 560 kWh

 

 

Water Consumption / Treatment Requirements:

 

The washing water re-circulates in a closed circuit.

 

The following quantities are re-circulated:

 

 

 

Washing water [lit/min]

Cooling water [Lit/min]

ML1400  Washing Machine

250 (hot water)

15

Turbowash

150

15

Tank

150 - 200

 

Centrifuge CDO 850

30

15

 

The requirement for water treatment depends on the dirtiness of the bottles. In case the bottles are relatively clean a simple system can be foreseen.

 

We estimate that about 5 m3/h of fresh water have to be added (2 m3/h loss during drying and evaporation and 3 m3/h have to be discharged to the public water treatment plant).

 

 

OCI GmbH
Baarerstrasse 95, CH 6301 Zug, Schweiz
GF: Hubert v. Navarini, Dipl. Ing.
Tel +41 81 3531685 / Fax +41 81 3535109
navarini@navarini.com
Officine Meccaniche Costarelli s.r.l., Perugia (I)

 

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