In 2015 MEP were asked to produce a report on the existing sand plant operating at Brett Aggregates Cliffe on the former Blue Circle Cement site. It was reported that the plant was inefficient and that fine sand was being lost to the effluent plant.
Following our report and the approval of Brett Aggregates, MEP provided Cliffe with a new sand plant equipment including an MEP Cyclone manifold and a Polymer Make Up Unit.
The contract included the full process design, transportation to site, installation, commissioning and training
The plant upgrade has been a success for Brett Aggregates with MEP and Bretts continuing their working relationship on further projects such as Queen Mary Quarry and Newhaven.
The Process
The sand and water slurry collected in the sump is pumped using the existing pump to four new MEP Cyclones. The underflow of the Cyclones pass by gravity to the existing dewatering screen.
The overflow from the MEP Cyclones report to a new Water Control Box and is recycled to maintain the sump level and optimise water and power consumption.
The sand product is dewatered using the existing dewatering screen to minimise final product moisture.
The excess water, together with silts and clays, overflow the Water Control Box to a new Effluent Tank.
The effluent is then dosed with polyelectrolyte flocculant in the existing thickener feedbox, improving the clarity of the supernatent. The Polymer Make Up Unit (PMU) flocculant dosing causes the suspended solids to agglomerate and become larger and heavier which accelerates the solids settling and de-watering processes within the thickener tank.
The PMU draws neat polymer from an adjacent IBC using a neat polymer pump, the polymer is mixed with water supplied at a pre-determined rate and delivered to the mixing tank. The water flow can be adjusted with a manual valve. The PMU control system also provides an IBC low level warning to allow the site time to replace the IBC.
The settled solids collected within the thickener are then pumped using a positive displacement progressive cavity pump to the sand dewatering screen.
