Recycling & Waste Management
delivered on time, on budget and produce the highest quality materials. The first step of the ProMan process is the appointment of a project manager who will act as the dedicated single point of contact for the customer. This ProMan takes responsibility for all aspects of the project including plant design, production scheduling, transport to site, installation, commissioning and final sign off.
In the background the project team works to ensure that all the commitments given to the customer in the project plan are met. “Regular, effective and meaningful communication with the customer is central to the ProMan process,” explains Sean Kerr. One of the key facets of the ProMan process on the Grundy and Co project which ensured clarity on what the outputs from the processing plant would be was the development of a performance statement relating to the final product specifications. “The willingness of the CDE team to enter into the production of a performance statement demonstrated a confidence in their technology which automatically gave us more confidence that the plant would do what it says on the tin,” says Sean Parry. “In our experience it is also extremely unusual for a company to do this, especially when dealing with construction and demolition waste material as a result of the variations in feed.” The performance statement for Grundy and Co covers the specification of the final products in relation to particle size distribution as well as final moisture content and optimum plant capacity. “Since final commissioning the products are meeting the specifications as laid down in the performance statement,” says Sean Parry. “This consistency allows us to command the best commercial value for our products.”
The CDE recycling plant includes a number of treatment phases including the initial feeding system, attrition, aggregate screening and stockpiling, sand washing, primary stage water treatment and a sludge management.
Material is delivered to the feed hopper with a 150mm grid. The integrated belt feeder then transfers material to a transfer conveyor fitted with an overband magnet to remove ferrous metals, which are subsequently discharged into a skip. Material is then discharged to the AggMax 150SR integrating pre-screening, the Rotomax RX150 logwasher, a trash screen and an Evoscreen dewatering screen for post-attrition rinsing of the material. The pre-screen consists of a 2.4m x 1.8m (8x6) dewatering screen fitted with polyurethane panels and allows for initial liberation of fines before material is sent to the Rotomax. The Rotomax is a twin shaft design with a single gearbox. The attrition within the system is generated by the 138 individual blades constructed from chrome molybdenum. “This is the same steel specification as used in impactor crushers,” explains Sean Kerr of CDE. The blades on the separate shafts within the Rotomax dovetail with each other ensuring the maximum amount of material on material contact. The Rotomax is also equipped with side and rear discharge points for the removal of water, sand and silt.
Removing contaminants
As the plant at Grundy and Co is processing construction, demolition and excavation waste material it contains a proportion of contaminants which need to be removed including plastics, polystyrene and wood. These are floated off the back of the Rotomax and delivered to a trash screen. The +5mm material is discharged from the Rotomax onto a Evoscreen dewatering
52 Solids & Bulk Handling • November 2010
screen. This ensures that any minus 5mm material that has escaped capture is now removed from the aggregates and sent to the sand washing phase. A conveyor moves material from the system to a Prograde P260 dry sizing screen. The recycled aggregate products are classified into 5mm to 10mm, 10mm to 20mm, 20mm to 40mm and plus 40mm and discharged into bays. The top deck of this dry sizing screen has a rubber deck, while the bottom deck is polyurethane.
The minus 5mm material from the AggMax is sent to the Evowash 102 sand washing plant. Material is pumped from the sump through the 625mm cyclone and is then discharged onto the split dewatering screen where a 0-4mm coarse and a 0-2mm fine sand product are produced. Hydrocyclone technology on the Evowash is the most effective means of removing the unwanted minus 63 micron material from the sand product. From a typical level of 15% minus 63 micron material in the feed, this is reduced to less than 3% in the coarse sand product. One of the common features of the construction and demolition waste recycling plants installed by CDE is the inclusion of primary and secondary stage water treatment. Unlike traditional quarrying operations, it is generally the case that those purchasing a CDE recycling plant are located in built up urban areas. Not only does the limitation on space in this type of environment necessitate the inclusion of full closed circuit water recycling, but the health and safety risks associated with ponds or lagoons render them unsuitable for urban locations.
www.solidsandbulk.co.uk Prograde dry screen and aggregate bays
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