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Derwen Construction look to the future with CDE

CDE have recently supplied and installed a complete construction and demolition waste recycling plant for West Glamorgan-based Derwen Construction. Located on the outskirts of Swansea, the plant is the first of its kind in Wales and offers a viable alternative to waste disposal at landfill sites.

Highly varied feed material is now being processed by the CDE plant at a rate of 150 tonnes/h, producing high-quality washed, sustainable and certified aggregates that conform to British and European standards. The plant is also contributing towards minimizing waste to landfill, and meeting ever-increasing landfill division targets.

Material is fed on to a vibrating head mounted over the feed hopper to remove any oversize. From here an integrated CDE hopper/conveyor feeds the material directly into an R2M60 1.5m x 4.0m rising screen. An overband magnet is fitted to the inclined conveyor to remove any ferrous material.

The rinsing screen removes any –4mm material, which travels directly to a CDE Dual Sand plant and is washed using an integrated hydrocylone to remove the silts and clays. The Dual Sand plant is capable of producing approximately 80 tonnes/h of fine sand and coarse sand, typically dewatered to less than 13% moisture content.

Waste water is sent for treatment, first to a T-08 high-rate thickener with integrated polyelectrolyte dosing station. Here, a thick sludge is quickly formed and pumped to a holding tank equipped with agitators. A CDE/Diemme GHT filter press is then utilized for maximum water recycling. Used in numerous installations throughout the world, the GHT is a heavy-duty machine with a short cycle time that produces a cake dryness of around 80%. This results in easy handling and reduced transport costs. Moreover, no additional flocculant or lime is required, which significantly reduces long-term costs.  

Said to be one of the biggest filter presses currently in operation in the UK, the GHT press installed at Derwen is approximately 15m in length and processes around 15 tonnes/h of dry solids. CDE say Derwen provides an excellent example of how a GHT filter press can be utilized to great effect in an urban-based quarry, completely eliminating the need for settling ponds and significantly reducing the amount of surface water at the site. Recycled water from the thickener and filter press is sent to a water storage tank for subsequent recirculation around the system, reducing the site’s fresh-water requirements to a small amount of top-up only.

Meanwhile, all of the +4mm material from the R2M60 rinsing screen passes into an 8m long Rotomax 132/8 log-washer, where aggregate and dirt-bound materials are cleaned through attrition. Plastics and organics are floated off from the rear of the machine and passed to a small trash screen that returns any water and fine material to the sand washing plant. The scrubbed coarser material is fed directly into a D2M75 1.5m x 5.0m screen with a wet and dry split to produce clean 6mm, 10mm, 20mm and +40mm aggregates. Any –6mm material is fed back to the sand plant for coarse sand production.

CDE Ireland Ltd, Ballyreagh Ind. Est., Sandholes Road, Cookstown, Co. Tyrone BT80 9DG; tel: (028) 8676 7900; fax: (028) 8676 1414 


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