First Gennaretti centrifuge installed at Ellel Crag Quarry

Ellel Crag Quarry, which is located approximately 7km south of Lancaster, has become the first UK recipient of a Gennaretti centrifuge system. Supplied by Coventry-based DUO Equipment, the centrifuge forms part of a complete turnkey Powerscreen washing and water-management plant, which is allowing Ellel Recycling Ltd to produce 100 tonnes/h of clean, washed recycled sand and aggregate.

As water management was an essential part of the project, DUO Equipment, in conjunction with their partners Gennaretti, supplied a GHT 503 variable-speed centrifuge system capable of producing a dry silt cake at rates of up to 15 tonnes/h. Particularly suitable for recycling operations, Gennaretti variable-drive models are compact in design, relative to their output capabilities, and efficiently process sludge with variable solids content, such as that derived from washing recycled aggregates.

As well as the centrifuge, which is housed within a containerized unit, the water-management system includes a foul-water pump, a 6m diameter deep-cone thickener tank with pneumatic discharge valve, an automatic flocculent mixing and dosing station, a sludge buffer tank, a fresh-water tank, and all the necessary support framework, structures, walkways and access platforms.

Waste water containing –75 micron material from a Finesmaster 120, which forms the sand processing element of the main washing plant, is pumped into the thickener tank where the sludge drops to the bottom of the cone, while the clean water weirs over the top of the thickener and into the clarified water tank for subsequent recirculation and reuse by the washing plant.

Meanwhile, the underflow from the thickener is pumped, via the buffer tank (with internal rake), to the Gennaretti system, which subjects the solution to a centrifugal force that separates the solids from the liquids and conveys them, via an internal screw arrangement, to the discharge end of the unit. Water exits through the opposite end of the centrifuge and is pumped back to the thickener, while the dry silt cake is fed by screw conveyor to a stocking bay for disposal.

The silt-management system supplied to Ellel Recycling is a fully automatic, closed-looped system that recycles as much water as possible back into the wash plant, taking into account such factors as the silt content, clay content and settlement rate of the raw material. The system was specifically designed and sized for the process by DUO Equipment, in order to minimize operator input and maintain low running costs.

Installation of the new washing plant and water-management system has proven very beneficial for Ellel Recycling, who now sell three BS-specified aggregate products (–40mm +20mm, –20mm +10mm, and –10mm) as well as two sand grades.

Commenting on the project, director Peter Slater said: ‘We are very pleased with the materials that are coming off the plant, which are up to the high standards required by the construction industry. The Gennaretti centrifuge is proving to be an excellent piece of equipment, providing a dry, manageable cake while keeping up with production.

‘Our target was to produce high-end recycled aggregates, which we are doing; the challenge now is to increase our presence in the market and establish recycled aggregates as an alternative.’

DUO Equipment, 4 Rye Hill Office Park, Birmingham Road, Allesley, Coventry CV5 9AB; tel: (0845) 222 2386; email: [email protected]; website: www.duoplc.com