rPET Manufacturing Plant
Plastics is an umbrella term for different kinds of polymers. Individual polymers have different properties which make them suitable for ranging applications from soft drinks bottles, to oven trays or strapping, all the way through to fibre used in duvets or clothing. The same polymer can be recycled many times and here at Clean Tech we aim to play our part in the circular economy by processing post consumer PET bottles into the raw materials used in new plastic packaging.
Stage 1: Sorting and granulation
Crucial to our operation is our technologically advanced sorting plant. Firstly, any ferrous metal is removed. This is followed by the removal of smaller particles and flats (paper, cardboard, film etc.) through a ballistics separator and non-ferrous metal via an eddy current.
The next stage is sorting. Clean Tech’s 25 Titech machines sort up to 20 tonnes of plastic bottles per hour by polymer and colour, through harnessing the power of NIR (near infra-red) light and perfectly timed jets of air.
The Titechs are configured to allow the recuperation of the highest possible amount of PET. The recovered PET falls into two categories; clear (80% clear and 20% blue) and Jazz (all other colours). It is then sent onto one of our four granulators to be ground. Each granulator is configured to create evenly sized flakes, small enough to flow smoothly through all manufacturing in-feed pipes.
Stage 2: Washing and further polymer segregation
After granulation, the flake passes through a cyclone to remove excess dust and labels. The remainder of the contaminants (e.g. glue, labels, sand and grit) are removed through our hot wash process. Through a combination of friction washing, sink float chambers and screens, contaminants are loosened and cleaned off and polyolefins (caps and labels) are separated as a floating fraction.
The water and flakes are heated to approx 95°C, starting the food grade sterilisation process. We use our cleanest water at the end of the washing, where clean flake is removed, to make our water use as efficient as possible.
The flake passes through driers and an air classification system, removing yet more fine waste, dust and labels thus improving the quality of the PET flake. Our quality team continually samples the flake, ensuring production of the correct specification. The last part of the process is the combination of supplementary ferrous/non-ferrous metal removal and further colour and polymer sorting on the washed and dried flake; effectively Clean Tech’s secret recipe.
Stage 3: Extrusion
This is the final stage of the process, where rPET flake is extruded into rPET pellet. rPET pellets are then used to make preforms – the first stage of new PET bottles. Flake is fed into a heater, which rotates and heats it up. External heat is also applied, heating the flake for at least 60 minutes, causing the flake to melt and removing all the water in order to achieve a better intrinsic viscosity (IV).
Once extruded through a number of screens and a rotary die, the pellet is cooled by water, before entering SSPs (reactors) in order to remove all volatile compounds, resulting in the food grade quality of the final product.