Local engineering specialist Procon has completed the installation of a $1.1 million water separation system for international mining giant Vale’s S2-billion Moatize coal – mining project, in Tete, Mozambique.

The system was installed in October and has been operational since then; however, the project will be completed in March, following the integration of a specialized TD-4100C oil-in-water monitor designed by flourometer manufacturer Turner Designs, of California, Procon MD Andy Miller tells Mining Weekly.

"The monitor is designed to constantly test for hydrocarbon presence in water, and is able to provide up to 600 readings a minute," he explains.

Procon’s scope of work involved the installation of the ES 100 Ultraspin water separation system, designed to treat 110 000L/h, which is first received from the wash bay in two separate spill basins, each containing two skimmers.

The water and oil emulsion runs down into the spill basin from where the oil is separated from the water by the four skimmers and the Ultraspin hydrocyclones. The oil-in-water monitor is built into the programmable logic controller that is integrated into the overall control system. This ensures that effluent is constantly decreased before water is discharged into the environment or reused at the wash bay.

Miller points out that the Ultraspin separator works on a simple principle, whereby the oily water is pumped tangentially into the large-diameter end of the separator, which initiates a spinning vortex.

"The spinning vortex is accelerated as the oil and water emulsion moved down the tapered separation tube, transporting the water to the outside walls, while the oil moved to the center as it is lighter," he says.

The separated oil is then removed using the separator face and the treated water is discharged at the other end of the tube.

Unlike plate-pack style separators, Miller notes that the Ultraspin separator does not rely on weak gravity forces for separation.

"The centrifugal force generated inside the vortex of the Ultraspin separator is around 1 000 times greater than gravity. With such force, even emulsified oil droplets can be separated," he says. The hydrocyclone technology is able to remove 95% of 10 µm oil droplets from the water, which can then be recycled for heavy vehicle washing. This can result in as much as an 85% water saving and also eliminates potential hydrocarbon pollution that can occur downstream without the use of such a system.

Moatize, which is Vale’s largest operation to date, is expected to yield a yearly production capacity of 11-million tons of metallurgical and thermal coal.

Vale officially began mining activities at Moatize in May last year. The first shipment of 35 000t of thermal coal left Mozambique on September 14, after being transported for 575km along the Sena railroad to Beira, from where it was exported. This was the first operation of its kind on the railroad in 28 years.

Miller notes that the main challenges of the project are planning and logistics.

"Moatize is situated in a remote location and is, therefore, a difficult site to access. Significant logistical preparation and planning were undertaken to ensure that there were no unnecessary project delays," he explains.

Procon will be providing comprehensive onsite practical training on the Ultraspin separator, as well as theoretical training.

"We will ensure that a qualified technician is available on site for 30 days to ensure that all relevant mineworkers are provided with the necessary skills and expertise to operate the system at maximum efficiency," adds Miller.

From Mining Weekly, 23 March 2012, p37. By Gia Constella, features reporter.