May 31, 2013
DUO PLC, a Terex Washing Systems (TWS) global distributor, has installed a custom Terex sand and gravel washplant at the Readymix West Indies (W.I.) site in tropical Valencia, Trinidad.
The customized TWS plant processes the clay bound sand and gravel to produce three aggregates and one grade of sand on the 520-acre Readymix W.I. site.
The new DUO/TWS washplant replaced an existing plant that was challenged with inefficiencies and maintenance and production issues.
The new washplant is generating four grades of product–including zero to 6 mm of sand, 6 to 10 mm of aggregate, 10 to 20 mm of aggregate and 20 to 75 mm of aggregate–operating at 200 tons per hour. Site production consists of 60 percent sand, 30 percent aggregate and 10 to 15 percent waste (silts pond).
Readymix W.I. processes sand and gravel for concrete manufacture, block manufacturing and asphalt specifically for their use and also available to the general public. All end products are currently used on the island of Trinidad, though Readymix is considering working with DUO on a second Terex washplant as export markets develop.
The DUO/TWS washplant set up:
Natural clay bound sand and gravel feed material is first delivered to an H 9 feeder vibrating grid which removes the 100m+ material. The inclined lattice frame feed conveyor, which was design and built by DUO’s manufacturing division, then delivers the material to the 206R -2 deck rinsing screen to get an initial effective grading. At this stage, the top deck removes the +75 mm material, which is stockpiled using a TC4026 conveyor. The bottom deck removes the 6 mm to 75 mm material, while the material below 6mm is pumped into a FM 200C cyclone, where a zero to 6 mm instantly salable sand is produced.
The Terex FM 200C cyclone is a sand recovery unit with a centrifugal slurry pump, twin hydrocyclones, a collection tank and a 14-by-6 dewatering screen. It is capable of producing one or two grades of sand; in this particular plant the customer has opted for one grade.
Due to the high and varied levels of silt content in the material, the aggregates require additional scrubbing to help ensure it is cleaned to specification, which is achieved through the PS 200R washer unit. This system is specifically designed to work in the recycling industry but can be easily adapted to work in gravel applications.
Dewatering screens are fitted to either end of the machine, which consists of a trough and two spiral axles, counter rotating to each other, with exchangeable blades to intensively scrub the feed material. Friction from this process breaks down clay conglomerates and allows scrubbed material to be stockpiled.
Once the aggregates pass through the PS 200R washer, they are then discharged onto a second DUO lattice frame conveyor. These 6 mm to 75 mm aggregates are delivered onto a onto a 165D -2 deck dry screen to achieve a three-way split, classifying material into the customers desired grades: 6 to 10 mm, 10 to 20 mm and 20 to 75 mm.
At this point the washplant uses settling ponds for its dirty water. Dirty water from the FM plant, which contains material below 75 micron (silts/clays), is sent to a series of ponds. The ponds are set up so that the silt drops to the bottom and clean water weirs over the top, producing clean, reusable water. In the future, it may be possible to incorporate a Terex water treatment plant to eliminate the need for ponds altogether.
The entire plant is controlled and monitored from a central PLC electrical control panel housed within an ISO 20-foot container. The panel is programmed for automated startup and shutdown sequences and was fully wired and programmed before leaving the factory.
DUO supplied a comprehensive set of civil drawings allowing for site work to be carried out well in advance of the plant arriving on site. The AutoCAD and 3D drawings pinpointed where each piece of equipment would sit on the concrete plinth. The drawings also showed details for electrical conduits, fresh water supply and dirty water disposal.
The wash plant has been in operation for one month. Ravi Singh, quarry manager for ReadyMix W.I. said, “We are extremely impressed and excited about the prospects of this new DUO/TWS washplant, which is currently operating at 200 [tons per hour]. We can firmly say this is the largest project the company has embarked on for a long time…”
Check out the photo gallery below for an up-close look at the custom washplant.