In 2017, MEP were selected by Brett Aggregates to supply a sand and gravel washing plant as a part of a project at Queen Mary Quarry to replace the existing plant that had been in operation for over 40 years.
Centristic were the Principle Contractor, and a team made up of MEP, Centristic, Leicester Electrical Services, Sandvik and Vision successfully supplied, installed and commissioned the washing plant.
The design of the plant allows for the wide variety of gradings that Queen Mary Quarry processes.
The Process
The plant has two feed hoppers and feeder conveyors. These discharge onto the feed conveyor, which is fitted with a clay
picker, an over-band magnet and a metal detector. The sand and gravel together with wash water is collected in a boiling box and is discharged onto a triple deck vibrating pre-screen complete with spray bars.
The material retained on the top deck of the pre-screen >100 mm (discard) will fall to a bay for removal by front-end loader. The material retained on the middle deck and the material retained on the lower deck is combined and passes to the feed end of the MEP Log Washer. The material passing the lower deck, < 4.00 mm in size, together with the water, passes by gravity to the first compartment of the Two Compartment Sump.
The coarse material discharged by the Log Washer passes to a triple deck sizing screen. The trash underflows from the Log
Washer to the MEP 3m Sieve Bend. Material retained on the top deck of the triple deck sizing screen, > 20 mm in size, passes by conveyor into a surge bin which is fitted with a chute and control gate to feed the crusher.
The crusher discharge falls by gravity to the crusher return conveyor and discharges onto the head end of the triple deck
sizing screen. Material retained on the middle (20 x 10 mm) and lower deck (10 x 4 mm) pass by conveyors to stockpiles.
The sand and water slurry collected in the Coarse section of the Two Compartment Sump from the pre-wash section of the plant is pumped using a centrifugal pump to two MEP Cyclones. The Cyclone underflow passes by gravity to the Coarse Sand De-Watering Screen.
The sand and water slurry from the underside of the Coarse Sand De-Watering Screen flows to the Fines section of the Two
Compartment Sump. The slurry is pumped using a second centrifugal pump to four MEP Cyclones. The underflow passes by gravity to the Fine Sand De-Watering Screen.
The overflows of the Cyclones report to the Water Control Box where it is recycled to maintain sump levels and to optimise
water and power consumption. The sand products are dewatered on two screens to minimise the final product moisture. There is also an option to combine the fine sand into the coarse sand product or make to individual sands.
Excess water together with silts and clays overflow the Water Control Box to the Effluent Tank where is pumped to the lagoon.