What happens at a Materials Recycling Facility? (MRF) – How does our sorting machine work?
Unsorted mixed waste is transported to Envirohub
from around the county and is emptied out at the plant. From the ground, it is lifted
by a mechanical grabber and placed into the hopper where it is shredded down to a maximum
size of 300 millimetres. The shredder is fitted with an adjustable setting to ensure an even
feed and spread of materials across the belts on the whole plant. This is necessary for
the advanced optical technology used in the plant to view and sort the waste efficiently.
From the shredder the waste is fed via a long incline belt to the trommel screen. This big
drum tumbles the waste to separate all fine material such as soil and dust, and organics
such as food waste, which would otherwise contaminate the recycled products. This filters
out of the base of the trommel and will be turned into a refuse-derived fuel product,
known as RDF. Everything else continues on to the ballistic
separator. The rotating paddles on this belt walk everything upwards but only the two dimensional
material makes it over onto the next sorting line. The three dimensional items can’t make
it to the top and fall back onto the 3D line below.
From the top of the separator, the 2D material now falls onto the accelerator belt passing
under the first optical sorter. The optics are positioned over the belt and recognise
the different classes of material. Here, this optic is set to separate soft plastic film.
When it sees an item of soft plastic approaching, it triggers a jet of air which hits the item
as it crosses the end of the belt, blowing it on to the conveyor that sits behind the
optic hood. From there, it passes to a hand-picking belt where any contamination is removed. However,
the process is so effective that it isn’t usually necessary for this to be manned.
The material that is still on the belt after the first optic drops down onto the second
accelerator belt beneath. It then passes the second optic, which is set to select all paper
and card products, which fall into the bay behind the optic hood and down onto the hand
picking belt where any contamination is removed. Usually there are two people working on this
belt to ensure the highest possible quality. So back to the 3D material. Firstly, this
is conveyed past a powerful magnet which removes all ferrous metal . What remains is then passed
through the eddy current machine which removes all non-ferrous metals such as aluminium.
All metals are collected in the skips below. The non-metallic material left on the belt
then does two passes through the third optic. The first pass recovers plastic on one side
and the second pass recovers all paper and card on the other. Anything left will also
go into RDF. All the sorted non-metallic materials end
up in these bays below the plant. Periodically the contents will be baled and wrapped ready
to be transported.