Water recycling crucial for sand washing plant
A new sand washing plant from CDE Global has recently
been installed in the Kingdom of Saudi Arabia for the Abdullah Abdein factories for cement production. The plant is located in Tabuk in North West KSA and includes an EvoWash 151 sand washing plant and an AquaCycle thickener (Fig.). The 150 t/h washing plant is processing a combination of dune sand and crushed limestone and gabbro in order to produce material for use in a new block making factory and ready-mix batching plant. This has resulted in significant production efficiencies for Abdullah Abdein Bukhary as they were previously buying in the sand required for these operations. The project for Abdullah Abdein was delivered in partnership with the Middle East Development Company (MEDCO) who has headquarters in Jeddah and a number of other offices throughout the Kingdom of Saudi Arabia in Riyadh, Al-Khobar and Abha.
A key factor in the success of this installation is the ability of the EvoWash to accept a combination of feed materials. Given the variation between the composition of the dune sand and crushed rock feed it was recommended that the 2 materials be blended prior to processing through the EvoWash. “By blending the materials the plant is able to deliver the required 150 t/h processing throughput” says Iain Walker, CDE sales manager for the Gulf region. “This is because the dune sand is a very fine material so if processing this material on its own the capacity of the wash plant would be reduced to approximately 120 t/h. Blending the 2 materials allows the customer to maintain the required capacity while also delivering high quality concrete sand.”
The feed material is delivered to the plant dry and the EvoWash comes equipped with the additional option of a feed box mounted on the side of the sump with an integrated water inlet point. This ensures that the material is adequately fluidised before it enters the EvoWash sump. The material is then pumped to a dual cyclone arrangement via the integrated Warman slurry pump. The cyclone underflow is discharged onto the EvoWash dewatering screen with the 63 µm material removed and is subsequently discharged to stockpile with approximately 12 % moisture content. The cyclone overflow containing the waste water and the 63 µm material is discharged to the water treatment phase which employs an AquaCycle A400 thickener. This allows for 90 % of the water used during the sand washing process to be recycled to the washing plant thus reducing the volume of fresh water required to feed the plant.
The AquaCycle thickener works by separating the waste water from the fine material with the assistance of a flocculant. Material enters the thickener and is dosed with flocculant prepared in the integrated FlocStation unit. From here the material is delivered to the centre of the tank in order to ensure efficient settlement of the fine particles. The flocculant forces the fine particles to bind together and sink to the bottom of the AquaCycle tank. The clean water overflows a weir at the perimeter and is then delivered to a holding tank before being re-circulated to the EvoWash sand washing plant. The settled sludge is conditioned for discharge via the quadrake system which ensures that the sludge is of a consistency that allows it to be pumped greater distances than would otherwise be the case.
