Dre Site A – Wash Plant
‘Live’ Head Feed
The feed material handled by the excavator comes directly from the screening of mixed aggregates and is a maximum size of 40mm down to dust. The material is loaded onto what we call the ‘live’ head where ‘grizly’ bars initially separate any larger aggregate that may have found its way into the pile. The smaller aggregates drop down through a mesh shaker screen and onto a conveyor belt. Any deleterious waste such as plastics, wood and fabrics are shaken off the end of the ‘live’ head.
The 40mm down aggregate is then taken up an inclined conveyor belt into the top of the plant to begin its journey of separation.
Arial View
As the screened aggregate reaches the top of the plant it is deposited into a ‘log’ wash. The paddles in the rotating washer knock off any clay or heavy soils stuck to the stone. The cleaned stone drops onto a ‘sizing’ screen that separates the aggregate into 10mm, 20mm and 40mm particles. The mixed muddy water is directed to the sand plant which in turn separates the solids into 0-4mm and 0-2mm sand.
The liquid slurry remaining is pumped to the trash screen which removes any non-aggregate material before sampling is undertaken and a ‘flocculent’ injected. This helps with a further separation as the slurry is pumped into 2 x upright silos to allow settlement. (these silos can be seen in the control room video)
Product Belts
At ground level we begin with the 10mm clean stone stockpile moving around to the 40mm and onto the 20mm.
From there we move around to the 0-4mm sand and the 0-2mm sand. It seems we can’t make enough of these 5 products as they head out of the gate on a lorry as fast as we can produce them.
As we make our way from the sand bays, we walk along the sealed drainage system that captures and water run off for re-use in the plant. Underneath the plant, we look into the Trash Screen where the flocculant is added, past the generator plant and around to the ‘cake’ (clay) bays where we can see the cake being dropped from the press above. This is the final stage of the plants process.
Control Rooms & Press
There isn’t a lot to see in the control rooms and this is significant because the whole process has been simplified to maintain the mobile nature of the plant. The controller only has a few electrical cabinets to monitor as he watches the plants progress through a conveniently placed window.
Moving into the press we can see the injection moulds and fibre bags where the solids from the settlement silos (that’s the two silver tanks you can see as we moved around) is injected into the bags. At this stage there is still an amount of water present which is squeezed out. The clean water is recycled for re-use within the plant. Nothing is discarded other than the small amount of deleterious material from the trash screen.
From the platform at the end of the press room we can see the lagoon that traps rainwater run-off. This water can be pumped back to the wash plant and or used as dust control during very dry periods.