Last-generation concrete reclaimer delivers efficiency and environmental gains for Irish concrete producer
Corcoran Concrete operate a concrete and mortar plant on the outskirts of Westport, Co. Mayo, an important fishing and tourist destination in the Irish Republic. Because their plant is located adjacent to a small river that runs through the town, owner Sean Corcoran was concerned about possible pollution from site run-off. This, coupled with strict Irish licensing laws surrounding waste disposal, led Mr Corcoran to take a proactive approach to dealing with concrete and mortar slurries and so he initiated discussions with CDE.
CDE have been researching and developing their concrete-reclamation system for almost three years with several prototypes and exhaustive design work. The company believe that the majority of systems on the market today are overly focused on heavy solids removal, often at the expense of poor recycled water quality and low-grade sand output. With their background in water and sludge treatment, CDE felt that a more efficient and complete system could be achieved.
The new installation for Corcoran Concrete is the first of the latest generation of Concrete Reclaimers from CDE. The unit has been designed to accommodate up to 4m3/h of –75µ cement silts, with the filter-press capacity as the limiting factor. This throughput is more than adequate at this particular site although larger presses are available. The screening element of the plant is able to handle a feed of around 20 tonnes/h, a capacity which is rarely tested on site.
Returned part loads of concrete/mortar and washouts are accommodated by the new plant. The concrete yard is benched to the main feed sump so that site run-off and rainwater can be handled. This sump is effectively a holding point for all material to be processed. Drivers simply flush out waste slurries to this point and hose down their vehicles. Coarser material begins to settle in the sump while dirty water runs off to the adjoining waste-water tanks, which are fitted with motor-driven agitators. Once the main sump is sufficiently full the site’s shovel driver starts the plant and enters the sump to lift out a load of the now relatively settled sludge.
This material is fed into a 7-tonne reception hopper, a unit specifically designed to prevent material from holding up on the internal slopes while offering a shovel-width feed point. A reject grid is fitted as standard. From here the slurry is fed directly to a CDE Dw-43s vibrating split screen mounted over a deep catchment box. The split-screen design offers rinsing (5mm mesh) and dewatering in the same unit. Spray bars fitted with polyurethane dovetail nozzles are fitted to the rinsing screen. No separate freshwater feed is required as the rinsing water is recycled from later in the process. Minus 5mm material and water pass this first screen section and discharge into the catchment box below, which in turn feeds a ground sump equipped with a Warman QV.65-SP sump pump.
A mesh protection panel is mounted over the ground sump to prevent the ingress of large particles that could cause pump wear or damage. A generous amount of headroom is offered by the design at this point to facilitate maintenance and washout of the plant. Minus 5mm slurry is pumped to a conical 250mm hydrocyclone where silts and the bulk of the excess water are removed. Sand exits the base of the cyclone, discharging to the dewatering portion of the screen before passing to stockpile in an adjoining bay at less than 12% moisture content.
The excess water and fines discharged from the cyclone pass back to the main feed sump. As mentioned earlier, dirty water constantly overflows this sump to the waste-water storage tanks, where two agitators keep the material in suspension. These agitators are removable to aid maintenance and periodic cleaning of the tanks. This holding area acts as a buffer, feeding a small header tank over a Warman 1.5/1 BAH slurry pump, which in turn feeds the filter press.
CDE chose a Diemme ME 630.1200 11-plate press for this application, which offers a total capacity of 1.16m3 per press. Diemme and CDE have worked in partnership since 2002, with CDE acting as Diemme’s official UK and Ireland dealers, and models ranging from 4 tonnes/h to 20 tonnes/h are now operating across Ireland and the UK. The press has a fully automatic cycle, ranging from 20min to 30min in this particular application. CDE offer an automatic cloth-washing system with most press installations but this has not been necessary in this instance. With each press cycle the unit releases approximately 2 tonnes of waste at around 80% dry solids by weight; this is easily disposed of by loading shovel. Clean water is discharged to a separate holding tank.
Output from the CDE Concrete Reclaimer is of high quality and commercial grade, and more than adequate for reuse in concrete batching. The sand especially is of particularly high quality without the high cement and silt content often found in such products. The fact that it is presented in a consistently dry form is an added benefit in what could otherwise be a messy process.
Sean Corcoran is clearly impressed with the new system, which has now been running for six months. He said: ‘The Concrete Reclaimer has proven itself to be highly reliable and has certainly improved the efficiency of our operation, as we can fully manage our own waste products. Another major benefit is that site run-off and rainwater have also been addressed with obvious environmental benefits.’