Pet

Baled bottles are fed into a bale breaker, and, transported by a conveyor belt equipped with metal detector to remove any metal present, are conveyed to the optical sorting system for further sorting.

Starting from loose bottles ,the sorting before granulation can be set up to sort out PVC, bottles by color and other “non bottles” items.

Once selected, the scraps contaminated with dust, sand and whatever else one can think of, are ground  with a single shaft shredder, a machine that doesn’t suffer much as far as wearing.

 

At this point material hits water for the first time as it is conveyed into a pre-washing machine.

The machine, working with an high quantity of water, together with the friction done by the high speed of the rotor, convert most of paper labels into pulp that, together with most of dirt, goes out with water. It uses plenty of water, close loop, going through a water filtering system simple and efficient at the same time. 

From the pre-washing machine flakes go into a buffer tank, sized for the quantity being processed, and provided with three different level controls.

From buffer tank flakes are conveyed outside by means of a screw conveyor and fall into the hopper of first sink-float tank where another screw conveyor push flakes under the surface of water to a stirrer to remove the surface tension of water from flakes’ surface.

In the water tank PET flakes sink, labels and caps float due to their lower specific weight, below the one of water. Floating materials are conveyed toward the waterfall at the end of the tank by means of the water flow created by a pump with the aid of rolls slowly rotating and pushing material forward. Extraction from the tank is by a screw conveyor with dewatering, delivering it to a centrifuge dryer and than, by a conveying system, to a final cyclone where material is separated from air and fall down into a container.

PET flakes, sink to an horizontal screw conveyor slowly rotating at the bottom of the V shaped sink float tank and are forced into another inclined screw conveyor for extraction.

The extracted flakes enter Caustic washing which is needed to remove the glue residue left by the removed labels. This part of the line include a preparation unit which is a continuous mixer to receive pre-washed flakes and keep them under chemical solution for a stated period of time.

The difference between the standard “mixing pot”, which is the most common device, for this operation, and this machine is highlighted by two main points:

-the guarantee of a stated residence time compared to the ”pot” where the last flakes fed into it can go out first and some others can reside into it theoretically forever.

-the chemical solution flows counter-current opposite to the flakes direction, in order to have all the time clean liquid toward the outlet, right before the flakes leave the machine, it is continuously extracted and conveyed to a filtration unit to remove glue and other residues before coming back to the preparation unit.

The washing machine after the preparation unit, has an electronic control by which operator states the amount of friction, and thus residence time, while flakes are kept under the caustic solution. By the friction rods of the rotor are making, water (the caustic solution) heats up increasing the effect of caustic and therefore decreasing the residence time needed to remove the glue. This proprietary technology does not require any external energy to heat up the solution. 

At the outlet of washing machines, flakes go straight to a centrifuge that removes the caustic solution from the surface of flakes and then blown to a second sink-float tank where the residual loose labels  are separated.

Sinking PET flakes are extracted from the tank and fed into the rinsing machine where fresh, clean, neutral water is used. This water, after neutralization, goes back to the system.

 

After the rinsing process flakes are fed into an horizontal centrifuge dryer for final drying till a residual moisture content below 1%.. 

Last device of the line, before final packaging, is a fines separator which works with an air counter flow lifting up, toward a blower with air flow control, fines and labels (if any), while helping to decrease the moisture content.

All the line is controlled by a PLC making all the process fully automatic.

Line starts and stop by pushing a single button, and during the starting sequence, controls also water levels, caustic soda concentration, temperature, water flows, water PH plus all the safety devices spread along the line.


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