Blower removes light materials from scrap flow

A novel way of removing light materials from waste and scrap is to use a blower providing a continuous curtain of air horizontally across a drop between upper and lower conveyors.

Air Control Industries reported that a novel way of using blowers for extracting 'lights' (light materilas) from skip loads of waste for more effective - and more financially rewarding - recycling has been incorporated in recycling plants at Southampton and North London, UK, by materials handling system designer and builder, McCloskey International.

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

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

Typically, when skips arrive at the sorting depots mechanical grabbers or operators remove large items, such as fridges and TVs.

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, such as clay, small stones, etc - might be used for making up ground.

At the next stage, the oversize material, such as larger than 40mm screen, is conveyed up to a picking station.

At the end of the conveyor the material is allowed to drop a distance of about 1m onto a second conveyor.

This is the first point where a blower is used extract the '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 then runs through a manual sorting station where wood, ferrous metals, aluminium, copper and plastics are extracted.

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.

* Blower types - the blowers used by McCloskey are forward bladed, centrifugal units supplied by air movement specialist, Air Control Industries (ACI) of Chard, UK.

ACI recommended centrifugal blower units because, when 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 15kW and 18.5kW blowers to McCloskey International together with complementary speed control inverters.

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