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Gaskell Bros, based atWinwick nearWarrington, have experience in boththe quarrying and recycling sectors.Their site, originally a quarry, is now

used for landfill and recycling.The majority ofmaterial brought in is building, demolition, andpublic service waste from the surroundingLiverpool, Manchester, and Leigh areas. Gaskelldirectors Mike Broad and Mark Gaskell saw anopportunity for washing this waste andestablished their first system in 1999 using thestandard aggregate and sand-washing systemspopular at the time.In 2002, however, Gaskell approached CDE

for a solution to the excessive fines losses theywere experiencing with their conventionalbucket-wheel system. CDE supplied a 40tonnes/h Compact Sands plant that improvedthe system’s performance with respect to finesrecovery and sand dewatering. In 2004/2005Gaskell decided to revise the complete

operation with a view to replacing the existingsystem that had suffered wear in the harshrecycled aggregates environment.After consultation with a number of leading

plant suppliers Gaskell opted for a newturnkey system from CDE. Mike Broadcommented: ‘I believe that this is the mostadvanced aggregate recycling system in theUK. I know of no other manufacturer capableof delivering such a complete system,specifically designed around my individual feedcharacteristics and output requirements. CDEoffered the complete turnkey package fromdesign to commissioning.We were regularlyconsulted and made important contributionsthroughout the project.’The system has to manage a widely varied

feedstock that can include plastics, paper andpolystyrene in addition to organiccontaminants such as soil, clay and wood.Whenthe plant is not washing reclaimed materials �

Turnkey Solution forGaskell BrosCDE supply advanced recycling system to the North-West

Gaskell Bros’ new processing plant from CDE

12 www.quarrymanagement.com QM July 2006

at a rate of 120 tonnes/h, it is employed towash the site’s own reserves of fine sand toproduce commercial-grade building sand.Waste is brought to site either by Gaskell’s

own fleet of vehicles or directly by customers.On arrival at the weighbridge the load isviewed via a remote camera to check thematerial’s suitability for the washing plant.Unsuitable loads are directed to Gaskell’slicensed landfill site while appropriate materialis diverted to the wash plant. Large pieces ofrubble are broken down using a pulverizerfitted to an excavator with the majority ofmaterial then being transferred by theexcavator to a track-mounted jaw crusher.The feedstock first passes through a

vibrating head to remove +100mm oversizebefore passing to the feed hopper fitted withan integrated belt feeder and inclined conveyor.This new CDE product was specificallydesigned to facilitate and speed-up installationand is delivered as a single unit.A further

advantage is that the hopper’s belt feeder andthe inclined conveyor are precision alignedduring manufacture, significantly reducingpotential spillage and housekeeping problems.Ferrous metals are removed by an over-bandmagnet mounted on the inclined conveyor asmaterial is transferred to an R2M90 1.5m x 4mrinsing screen.Any –5mm slurry is passed to aCompact Sand plant that removes silts and claybelow 75µm via an integrated hydrocyclone.The sand is typically dewatered to less than13% moisture content.This approach tocommercial-fines recovery means that there isno need to pre-screen or remove topsoil fromthe feedstock.This increases the number ofpotential saleable products by offeringdewatered sharp sand that finds a readymarket as cable and pipe bedding as well as innon-structural concrete manufacture.As with any washing plant, properly

managing the waste water is crucial, and inrecycling systems this presents a technicalchallenge in view of the highly variedfeedstock. Here a CDE high-rate thickenerwith an integrated polyelectrolyte dosingstation is used.This rapidly settles out theexcess fines to form a dense sludge that isthen pumped to a remote bunded settlingarea. Clean water overflows the thickener andis filtered to remove any residual floatingcontaminants, such as styrofoam particles,before being passed to an adjacent storagetank. From here water can be readilyrecirculated to the washing system.In August Gaskell’s will take delivery of a

new 16m overhead-beam filter press capableof handling up to 30 tonnes/h of waste solids.This will complete the water-recycling circuit,creating a fully closed system with only dry,easily managed cake output as a by-product.This unit will be the largest machine of its typein the UK.The overhead-beam design was firstused by CDE for a recycling project near

Right: Feedstock material

Far Right:Washed aggreagte

Stockpiles of washed buildingsand in the foreground andrecycled grit in thebackground

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Birmingham where it is proving much morerobust than conventional sidebar presses. Itsintegrated washing system and fully automaticoperation means it is particularly suited to thehighly variable feed volumes andcharacteristics found in recycling projects.Referring back to his ongoing relationship withCDE, Mr Broad noted: ‘When it came toselecting the supplier for a heavy-duty filterpress to complement this system CDE werethe natural choice’.Aggregates and dirt-bound particles pass

directly from the primary rinsing screen to an8m CDE 132/8 Rotomax log-washer.Thisfeatures twin shafts fitted with chromo-molybdenum blades; each shaft has a diameterof 1,320mm tip to tip.The speed of theRotomax is easily controlled to accommodatechanging material characteristics as the unitfeatures a single motor and gearbox. MikeBroad is particularly impressed with this unithaving worked with several log-washers fromother suppliers.This has been highlighted bythe unit’s exceptional wear performance;blades have so far returned more than fivetimes the wear time of units previously usedby Gaskell. Light contaminants includingclinker, plastics and organics, such as wood andgrass, are actively floated off from the rear ofthe Rotomax before being passed to a trashremoval screen that recovers water and fineparticles to the sand-washing unit.Attritionedmaterial is discharged to a dewatering screenfitted with CDE’s modular PU panels.Liberated fines and water pass through thisscreen to a ground sump complete withsubmersible pump.The sump also collectswash-down and groundwater, which is thenpumped back to the rinsing screen,encouraging initial fluidization and reducing thefresh-water requirement while facilitating sitemanagement and safety.Dewatered +5mm aggregates are conveyed

from the dewatering screen to a D2M90 1.5mx 4m twin-deck dry screen for final sizeclassification.The process currently providesfive commercial products — sand, 5–10mm,

10–20mm, 20–40mm and 40–100mm — andthese are sold throughout the North-West.Most of the products are used for pipe beddingand cable-laying work with the 20–40mm alsosold as a gas membrane for new house builds.The +40mm is commonly used for pile cappingor can be crushed to produce recycled MoT 1product, as it is virtually free of plastic, wood,and other contaminants. Once the overhead-beam press is installed even the silt and clayfines are expected to find a market as puddlingclay for canal and watercourse lining.Themagnet-collected ferrous metals are passed toa skip to be sold as scrap.According to CDE, washing adds much

greater value to the final products thanconventional dry processes. The ability torelease quality sand that would otherwise be awaste by-product is another importantadvantage.This particular installationdemonstrates how the correct application ofthe latest washing technologies means thatwater availability and waste-fines managementare no longer significant barriers to efficientlyrealizing commercial products from formerwaste materials. It is now up to recycling anddemolition operators to decide how best tocapitalize on these new technologies, acommercial decision that has clearly paiddividends for Gaskell Bros. �

The rinsing screen, Rotomaxlog-washer and dewateringscreen

Far left: Light contaminantsfrom the trash removal screen

Left:The D2M90 twin-deckdry screen