Removal of 'Lights' from waste using air blowers

A novel way of employing blowers for extracting 'lights' from skip loads of waste for more effective - and more financially rewarding - has been applied in two UK recycling plants

These systems have been incorporated in recycling plants at Southampton and North London by McCloskey International, the materials handling system designer and builder.

'Lights' (paper, plastic, cardboard etc) can down-grade potentially recyclable waste material collected in skips.

So McCloskey has devised this technique for quickly and effectively removing them without hindering the sorting process using blowers.

Typically, when skips arrive at the sorting depots, large items, such as fridges and TVs, are removed by hand or by using mechanical grabbers.

The next stage would be to eliminate 'fines' or media smaller than 40mm.

This would be done by loading the material into a rotating trommel screen drum with either a mesh or pierced metal sheet with 40mm apertures.

This media - clay, small stones, etc - might be used for making up ground, such as gardens on building sites.

The next stage the oversize material i.e +40mm is conveyed up to a picking station.

At the end of the conveyor the material is allowed to drop a distance of about one metre onto a second conveyor.

This is the first point where a blower is used extract 'lights' by blowing a continuous curtain of air horizontally across the drop.

Caught by the blast of air, 'lights' are blown from the falling material into a collection bin on the opposite side of the conveyor.

The remaining material runs through a manual sorting station which extracts wood, ferrous metals, aluminium, copper and plastics.

A similar blast of air takes place as the last of media falls off the picking station conveyor.

This final removal of 'lights' ensures that the residual material is clean and can be used safely for hardcore, sometimes after being fed directly into a crusher for further reduction.

The blowers used by McCloskey are forward bladed, centrifugal units supplied by air movement specialist, Air Control Industries (ACI) of Chard.

ACI recommended centrifugal blower units because compared to other designs, on a size-by-size basis, they deliver the best air flow and pressure, ideal for blasting entrapped 'lights' from falling media.

"Because the ACI units are so efficient they are compact for their output performance", said Declan Dooley, European Engineering Manager, McCloskey International.

"Their compactness and mounting arrangement also means the blowers are easy to install whilst the fixing plate on the outlet facilitates the attachment of our specially fabricated air delivery nozzle".

ACI has supplied both 15kW and 18.5kW blowers to McCloskey International together with complementary speed control inverters.

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