FLSmidth has been awarded a contract to supply two elevated thickeners for the expansion program at Lihir Gold Ltd.’s (LGL) gold mine on Lihir Island in Papua New Guinea. Each of the two 7,500-m3/h-capacity thickeners will be 48 m in diameter and will be fitted with a hydraulically driven bridge drive, making them among the world’s largest bridge-drive thickeners. They will be designed and fabricated in Australia, supplied “piece large” to accommodate the restricted lay down and site construction areas on the island, and barged to site.

As part of the design process FLSmidth and LGL operational personnel combined to conduct an extensive testing regime to investigate underflow capacities within the range of ore blends the thickeners could be processing. These test results provided pointers to the overflow clarity and underflow densities that can be achieved.

In line with LGL’s requirements to maximize underflow capacity, the tanks will be elevated. This design, according to FLSmidth, will provide a minimum suction line below the pumps and significantly reduce the chances of underflow blockage.

FLSmidth noted that, along with improved operational efficiencies, the elevated tanks will also provide improved safety for site operational and maintenance personnel by allowing unrestricted access to pumps and associated equipment.

The overall design of the thickeners and associated operational equipment has also taken account of the proven high seismic activity around the general area of the mine. According to the company, the thickeners are designed to tolerate seismic events stronger than what is considered typical activity.  A massive, integrated steel network structure will support each tank and provide the gravity feed between the tanks as requested by LGL.

Shipping of the units was expected to begin in April with final commissioning scheduled for late 2010.